Using a sports inflator needle to apply compressed air to each air line individually, I am finding several oddities.
The first is certainly not unexpected: Several of the airpins are sticking. I think my best bet for these is to remove the two pinblock cover plates, blow gunk out of the lines, and clean and lubricate everything. Although the airpins have a hex socket in their top so they can be twisted to unstick them, every third airpin is obstructed by the rods that guide the pin jaws. I might try a ball-tip Allen key to turn these, but it is a pretty tight fit.
The next is that the I and 0005 pins appear to be swapped: applying air to one of these holes in the paper tower actuates the other airpin.
Finally, the mould signalling valve seems to use H and G together to signal the mould (and raising the H pin), but the documentation I have (the 2-binder ‘Monotype’ Composition Caster Manual) says it uses N and 0075.
I’m considering the possibility that I got some lines mixed up when I removed and replaced the bases for the Unit Adding or Unit Shift, but neither of these mechanisms uses G, H, or I (Unit Shift uses D, E, and F, and Unit Adding uses 0.005, 0.0075, J, K, and N according to the manual).
I will remove the Unit Adding dummy valve to identify exactly which lines lead where. Hopefully I can solve these mysteries.
It seems to me that the design choices of which lines control certain options never accounted for combinations of options that could have been useful in the future. For instance, the quadding and centering cannot be used to cast repeated characters from the A, B, or C columns of the matcase (it was only intended for quads, which are generally in the O column). The mould signalling uses N (at least, as my documentation states) and so cannot be used with 15×17 matcases because columns I and L would be inaccessible when signalling the mould (the N+I or N+L combinations would instead select column NI or NL). This is fine when it is used to select low quads but not when used to signal the side blade for a duplex or triplex mould; probably mats for duplex or triplex mould usage were only produced in 15×15 arrangements. Only the Unit Shift is designed in a manner that has no adverse impact on other functionality, but there is no reason why other options could not have been designed the same way.