Hi, Debbie!
It says "3rd NYC," and since the company is listed in another column, I'm going with C stands for Cavalry. The database of Andersonville Prisoners confirms this for Tim Connelly.
Name: | Connelly, TIMOTHY | Alternate spelling of last name: | CONOLLY | Year born: | 1844 | Rank: | PRIVATE | Company: | F | Arm: | Cavalry | Regiment number: | 3rd New York Cavalry | Date captured: | 6/29/1864 | Location captured: | Ream's Station, Virginia | Date of death: | | Cause of death: | |
| Fate:
Sent to Camp Lawton, Millen, Georgia, October 31, 1864. Mustered out November 29, 1865 at City Point, Virginia
Remarks:
SENT TO MILLEN, GA OCTOBER 31, 1864 |
There are multiple H. Cooks, but none from NY, but since he's in the Departures Book (you're a braver man than I am, for wading through that), I'm going with he fell through the clerical cracks in the database, which doesn't incorporate the departure or hospital records.
I keep meaning to tell you,since you only come up with a few departure dates - at Salisbury, outgoing letters are postmarked with just one or two dates on them (there was a fellow talking about prison postage at one of the Salisbury symposiums). The theory was that the date on the "stamper" that was used to postmark outgoing letters got stuck, and so they weren't able to change the date. Don't know if that might be what happened at Millen or not - you're way better at Millen than I am!
(Btw, I've been invited to go give another presentation in Andersonville at the POW Museum next year - I will really miss seeing you!)