Just saw and bought a base plug on QFA that includes a 'distance piece' giving a 3-sec delay (assume that this is arming delay rather than detonating delay given that the No. 69 is impact fuzed?)... I had no idea different base plugs existed and looked at the plugs on my No. 69s for comparison, which I found to be the standard ones. How many of these different base plugs were there then, and were a variety issued with the grenades in their crates? Maybe these were an experimental thing? Can't find any other reference to this beyond the QFA listing.