To be correct [pedantic I know ] it was a vertical dovetailed chopper lump not to be confused with a normal dovetail construction . These were pegged and soldered rather than brazed .Solidly made guns that BSA set out to make the cheapest possible English gun.
You will often see a small dot on the side panel ,this is a stopper covering a reinforcing pin through the head . This is not a repair but a factory fitting .