At Guildex (Stafford) I bought a couple of Tower Models 7mm O Gauge ‘Tower Power’ Shogun 5-Pole Canon Motor w/ Multi-stage Gearboxes. Although I didn’t know that’s what they were at the time, the price was right but I did note that they were each missing their final drive gear. In my view, the Canon Motors and fly wheels alone were worth the £25 each that I paid for them.

Enquiries on Western Thunder and the GOG forums, identified the product as described above and subsequently contacting Tower Models confirmed that there are no spares available.

One member of both forums happened to have a couple of the same gearbox units new and boxed he was very helpful in confirming that the gearboxes or at least his boxes were 25:1 ratio he also counted the number of teeth and confirmed that there were 29.
From further discussion it also revealed that San Cheng who produced them for Tower also used the same gearbox side frames for an 18:1 version of the gearbox using slightly different idler gears.

We ultimately came to the conclusion that the final drive gears are 29 tooth the Module is 0.3 and the diameter of the gear is 9.26mm