Thank you for this explanation - I also found this doc online, page 19 to 23 gives a really good description of the process and drawings of a Frankford Arsenal combination fuzeSome fuzes have horizontal slots in the outside base of the fuze for a wrench to tighten the fuze. This fuze and the M1907 look like a copy of older British “13 pounder” fuze...I don’t know the nomenclature off hand.
A powder train time fuse is time adjustable based on length of the black powder channel. If you look at the fuse parts, you will see small channels on the inside…these would be filled with black powder. The time setting markings should correlate to the length of the channel. Longer channel, longer time and is ignited when fired, usually by a weighted firing pin held back by a creep spring. This delay is intended for an overhead detonation before impact. If not, it’ll detonate on impact.
Damien, after doing some more research I think that you are absolutely correct about the Type 31 gun. This particular piece was found in Ukraine, and about one hundred Type 31 guns were sold to the Russian Empire in 1916. Also looking at the range and muzzle velocity it would make sense with a 18-second fuze.An interesting fuze. It and the Brit No.80 fuzes are based on the Krupp patented design, meaning that after WW1, Krupp made a lot from royalty payments from its former enemies. Business is business.
I would have thought it was for the Type 38 and 41 75mm guns, which used the Type 3 and Type 5 Time & Percussion fuses, but these are graduated for 22 seconds plus, not 18 seconds like the photos show. Still a mystery to me unfortunately, but it may be for the earlier and shorter range 75mm Type 31 Infantry and or mountain gun? cheers, Damien