wrote:
Could you please tell me the current catalog value for a Transvaal
#274a stamp. I recently discovered one in my collection.

There is no 274a Transvaal, only a 274aw, inverted watermark. The only
other variety 274b is also a watermark variety. Current price is in the
region of =A3250 for 274aw (used only - not listed mint) and =A3350 for
274b.

Cheers

Robert