Bill's got it right; although we can't yet say when the USSS discarded or stopped using their Tiffany & Co. mess kits, it seems that their individual methods of cooking was about homogenized as the rest of the army's was. Two quotes from Stevens' history:
"...notwithstanding the brisk fire under which they advanced none were hurt, but narrowly escaped the fast-flying bullets, one man being saved by his frying pan (for they carried their cooking kit always)..." - Stevens', page 340, describing the "Indian rush" on CS sharpshooters by 20 Michiganders from the 1st USSS, July 3rd 1863.
"...a Swiss member of Company A got the bottom of his frying pan knocked out on the back of his knapsack while faced firing to the left oblique. This made him very mad and he swore a lot of foreign oaths, worse than a trooper. For if there is anything that will make a good soldier swear, it is to lose his cooking kit." - Stevens, page 371, describing the 1st USSS advance at Kelly's Ford, Nov. 7th, 1863.
The usage of the word "kit" in these accounts seems to imply a collection of different cooking utensils/vessels instead of the mess kits that were issued with knapsacks early in their service. From many other sources the word "kit" is also used to describe a complete uniform ("rig" and "suit" also used) or a set of accoutrements/equipments.
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Brian White
Wambaugh, White, & Company
http://www.wwandcompany.com----------------------------------
Randolph Mess, U.S. Sharpshooters