Yep. That is the real thing. English flint. No way of telling how many gunflints were made out of it throughout the centuries, and still is. There is an almost identical chert in the Georgetown Texas area that has it.
Here are the only two original gunflints I`ve ever found. The French "blonde" flint on the left I found in Early County and the English flint on the right I found in Webster County. Both looked like they were from rifles. Flints for Brown Bess and French fusils were much larger.
The flake in the last two shots I knocked off a nodule of English flint and skinned and broke down a deer with. It also was very good for cleaning up the backstrap sinew.
In a lot of buildings. This is in Salisbury. This in particular was new made to look old but the old buildings had it also. Saw some foundations where it was used as aggregate for the concrete.