Had this vague hope on which regiment, since the 50th PA was in Beaufort, then had to scratch that. A photographer managed to take photos of them and their officers- this predilection for all grays put paid to that, mounts were bays, chestnuts, grays- mixed. Still, with a little research might be possible to discover who these men might be just based on that.
Charleston? Must look that up, may be something there. OH, anyone remember a photo of a clubhouse at one of these racetracks, used for an officer's prison? Was that Charleston?