It looks like the groove was cut using a two stage cutter or grinder which is quite unusual. Not that I'm into bayonets at all. Just that single 3/8" or so cut is simpler that 2x 3/16" cuts to my way of thinking. Brazing like that is what we call '.....snotty joints'! You can occasionally feel the blades loose in the socket. We were told to ignore what we saw as 'oil squeeze' type movement and only take notice if you could actually feel movement. Not that they ever really gave us any trouble - because they were rarely used! Unlike the troublesome No7 types!

Nice find Marysdad.