Joseph,
Loaded question!
Unfortunately my reference books and notes are in storage so I can't quite directly here, however I can answer this from memory and a few online sources. If I'm wrong about dates, etc. and someone else here can correct me, please do!!!
1862Berdan issued regimental orders during the Peninsula Campaign stating that during marches or when the men were going into battle in heavy marching order, knapsacks and other equipment were not to be removed. This is mentioned by New Yorker Harrison DeLong in a letter from the spring of 1862; DeLong was sick at the time and complained about the orders against removing knapsacks.
I recall that the companies deployed as skirmishers before the battle of Beaver Dam Creek/Mechanicsville in June 1862 were ordered to drop knapsacks behind the lines. After they were engaged in combat, many noted that they did not return to retrieve their knapsacks and thus lost them. Cyrus Hardaway, Co. D 1st U.S.S.S., makes note of losing his knapsack during this battle and having only one shirt and one stocking. In another account from the same battle it was said that only Companies C and G lost their knapsacks here as well so they may have been deployed to a different part of the line.
Brigham Buswell of Company F 1st, noted in a post-war memoir of Malvern Hill that he had done away with his knapsack and carried only a spare shirt, spare socks, and a sewing kit rolled up in a gum blanket (his uniform was "blue pants, an army blouse, and a cap).
Depew Swartout, Co. D 1st, stated in his diary on July 7th,
"Men are drawing clothing as most of them lost all in our six days march. Could not carry it" which to me implies that those who had knapsacks or blanket rolls containing clothing during the Seven Days campaign (which is what Swartout is referring to) had thrown them away. While he says that "most" lost their clothing, this could pertain to his company, his regiment, or more likely the entire army.
While the army was encamped at Harrison's Landing after the battle of Malvern Hill, Cyrus Hardaway again noted on July 30th that
"We had a circular read on dress parade advising the men not to draw knapsacks and no Extra Clothing to take advantage of the present chance to rest so as to be ready to march at a moments notice." Hardaway also mentions that the officers were permitted to carry no more than a complete shelter tent (two halves) around the same time.
On August 14th, while the 1st U.S.S.S. was still languishing at Harrison's Landing, Hardaway states that
"all the knapsacks and blankets were put on board the boats Sunday afternoon I think some of the boys will want their blankets before they see them again. I did not have any blanket but have a good overcoat that I found so I am all right for all the cold weather..."Presumably the Sharpshooters spent the late summer campaigns in light marching order; shelter halves and gum blankets only but no doubt discarded overcoats, blankets, and possibly even double bag knapsacks were picked up during colder weather. Allegedly the army was very poorly supplied with clothing, equipment, accoutrement, and shoes by the end of 1862. Wyman White, Co. F 2nd, noted that only a few men in his company were able to go on guard or picket duty in the winter due to the lack of new shoes (Wyman's own shoes were burnt up, falling apart, and he had tied the uppers to the soles by cutting thongs of leather from the opening edge!). It was in the late fall/early winter of 1862 that the knapsacks turned in on the Peninsula were returned...unfortunately, many men noted that they had been ransacked of diaries, photo albums, spare clothing, blankets, overcoats, et cetera, and some were even cut open with knives and destroyed.
I don't know if many new knapsacks were issued, or what kind of they were, however there no doubt would have been some extra knapsacks floating around. For instance, if 500 men turned in knapsacks during the Peninsula, and there were about 200 sick, wounded, disabled, discharged, etc., when the stored knapsacks were returned to the regiment in late 1862 there would have been a surplus. Men who had thrown theirs away and NOT turned them in would presumably been able to get one formerly owned by an absent soldier. Turning in knapsacks, blankets, overcoats, and uniform coats for storage (when ordered) was practical for the private soldier...in the case of uniform coats it meant that when it was returned to him later, he did not have to spend money from his yearly clothing allowance to draw a brand new coat.
1863The first quarter of 1863 saw massive reforms and restructuring in the Army of the Potomac. General Hooker eventually took command and after he did Sharpshooters quickly noted that drill, dress parades, inspections, etc. were happening on a daily basis. The first few months of 1863 saw the Sharpshooters in a mix of previously stored/returned and newly issued uniform coats, dark green trousers, dark green caps, and most notably leggings to replace the ones thrown away, sent home, or lost during Yorktown and the Peninsula. New knapsacks were issued but I am unaware of any document or purchase order showing that they were the same hair knapsacks made by Tiffany & Company in 1861/early 1862. But there is no doubt in my mind that some of the old "hair trunks" were still being maintained and used.
Before Chancellorsville the men in both regiments (and throughout the army) were loaded down with spare blankets, overcoats, uniform coats, fatigue blouses, trousers, and an abundance of underclothing. According to Wyman White, the day before departing camp saw the men turning in all of their spare blankets and overcoats; those who did not chose to box them up and literally bury them in anticipation of returning to the same camp after the campaign (in Wyman's case it paid off). Everyone entered the battle in full marching order; that is with knapsacks containing gum blanket, shelter half, wool blanket, and in some cases an overcoat. The men were also ordered to carry a full set of uniform with them (blouse and uniform coat), with many men carrying the uniform coat in their knapsacks.
Why the background on knapsack contents/uniform? Because both regiments were ordered to drop their packs near the Chancellor House and never returned to reclaim them. It's plausible that some men, who were a little wiser, might have kept their knapsacks but it's unlikely that this was widespread. Depew Swartout, Co. D 1st notes on May 6th that
"Lost all in battle all our things in our knapsacks and had nothing but a blouse to tent and sleep in," and the next day that,
"We lost all in losing our knapsacks."By the Gettysburg campaign, replacement knapsacks had been issued to the Sharpshooters. This likely occurred at the end of the second quarter in June 1863...possibly around the time the regiments boxed up and turned in any remaining green uniform coats and drew blouses for the summer campaign. On July 2nd Swartout mentions that "Got a shot in my knapsack" during the skirmish in Pitzer's Woods.
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Given the large number of Tiffany & Co. hair knapsacks issued in 1861/early 1862 and the casualty rate causing a
possible surplus of them to be returned in late 1862, it's not out of the realm of possibility to see a good portion of them in the winter of 1862/1863. However there is plenty of documentation from the Sharpshooters themselves stated that they were thrown away, lost, and destroyed throughout the Peninsula and Seven Days campaigns.
By 1863 there would have been a number left but you have to keep in mind that there is no record of new Tiffany & Co. packs being issued, and the ones that remained had gone through some hard field use and exposure. I suspect that by Chancellorsville there would have been a fairly even mix of hair knapsacks vs. double bags. However unless there is documentation to support the issuance of new hair knapsacks AFTER Chancellorsville, the vast majority of knapsacks issued after this would like be double bags.
I have little information from 1864 aside from Wyman White noting that one man in his company had to leave his hair knapsack behind in a bramble or be captured; the man left his knapsack behind and as Wyman put it, it was the last one in the entire regiment. There is also a Tiffany & Co. knapsack captured in late September, 1864, by Oscar Chappelle of the 12th South Carolina Infantry. This knapsack has a very worn stenciled name that has not yet been deciphered, although the museum believes that it belonged to a 1st Michigan Sharpshooter Regt. men...this is probably dubious though. I've always thought that it would be hilarious if this knapsack belonged to the man in Wyman's company but there is no way to prove it.
In terms of reproductions...if you're limiting your impression to what I call the "sexy" period of U.S.S.S. history, Yorktown and the early Peninsula, then you should have a hair knapsack. If you're going to a mid to late was impression then a double bag will work fine. However if you want to be flexible then you can have both!