Sounds like a Gordon officer's sporran, a silver cantle likely indicates it is a TA/Reserve officer's sporran as opposed to Regular/Active. TA regiments usually wore silver lace/braid/etc in lieu of gilt worn by Regulars. If so, its a bargain depending upon overall condition and possibly a gift as MacMillan said.

What's the name of that shop again?? ;)

The cones for the two black tassels will vary from black leather covered or engraved metal ones as in the pic below, but does it look similar to this perhaps...