It is possible to make a banana shaped lock using a left handed siler lock and making a new lockplate out of sheet metal.
I made the locks below for a pair of Swedish officer pistols. All the parts expect the lockplate are from the small siler lock. To get the banana shape the tumbler had to be placed lower on the lock plate in relation to the pan.
1.Fit the pan to the new lockplate blank.
2.Take a compass and measure the distance from the middle of the pan to the middle of the tumbler hole. Put one compass leg on the middle of the pan and rotate the other on the new plate to find the new center for the tumbler hole.
3. Mount the rest of the parts on the lock plate
4. Adjust the parts so the lock works. You will have to shorten the hook on the main spring and the toe of the tumbler were it rests. Likewise the angel of the shoulder of the cock and the
angel of the frizzen toe has to be adjusted.
I was surprised how far the the tumbler could lowered and still make a lock that sparks great.