Your Kerr's serial is not the 280 - that is an assembly number used on the various parts as they were hand fitted to your Kerr so that they could be kept together when taken apart for finishing, etc. The real serial is the 9552 which is on the frame and the cylinder. The Pratt Listing shows that in Co. H of the 18th Virginia Cavalry on July 6, 1864, that company had these Kerrs:

9240 - KERR - 070064 - CO H 18TH VA CAV CSA -
9740 - KERR - 070064 - CO H 18TH VA CAV CSA -
9927 - KERR - 070064 - CO H 18TH VA CAV CSA -
9949 - KERR - 070064 - CO H 18TH VA CAV CSA -
9955 - KERR - 070064 - CO H 18TH VA CAV CSA -
9961 - KERR - 070064 - CO H 18TH VA CAV CSA -
9974 - KERR - 070064 - CO H 18TH VA CAV CSA -

There is no other known war time listing that shows what serial Kerrs any particular unit had.

I woudl be very interested in seeing photos of the holster - I have seen several types of old holsters with Kerrs fitting into them, and I would like to see a photo of yours.

Jeff