It would be unusual for a half-stock rifle with a Goulcher lock to have been flint originally.
It is not unusual for various dealers, including major auction houses, to state that obviously original percussion rifles had been converted from flint. Affects the confidence one has in their other statements.
The easiest way to tell if the gun had been flint is to look for the extra holes in the lockplate, one for the frizzen, two for the frizzen spring. They may be left as holes or plugged.
Of course if the gun had been converted by putting on a complete new percussion lock, there will be no holes. In that case one looks for the cut-out behind the hammer, where the former flint cock came to rest on the plate.
Most commonly - but not guaranteed - flint locks were held by two screws, and percussion locks by one. I suppose - suppose - this is because the drum or patent breech on a percussion gun also serves to resist the mainspring torque.
