All locks were made by hand until mid 19C, using shears/guillotine, fly press, and drill, and hand tools.
Cabinet locks often had the bolt head divided into 2, 3, or 4 bolts - nobody now knows why this extra work. Wheel wards were common, on the backplate, or cap, or both. Cap was usually riveted on, screws were expensive.
Many cabinet locks (back action) don’t have even a single tumbler. Instead, the top of the bolt has a strip split outwards by chisel, to act as a spring; this and the bolt tail protrude through a slot in the lockcase, and another notch is cut, next to the talon for the key. Such locks are not latches, but the bolt can be pushed in by heavy end-pressure, without damage - can be a useful method of opening cheap cabinet furniture.
Older locks have neatly bevelled edges to the backplate, and curiusly, French locks have larger fixing holes nearer the bolt head than the other two. European cabinet locks also are often double-throw, and have bulleted keyholes, often with a nozzle.
Old cabinet locks are handed, and there was no standardisation of sizes, beyond the lengths of the backplate, as 2″, 3″, etc. Willenhall made vast quantities of cheap cabinet locks, many being exported. An apprentice boy would handmake 1 gross a day!
As Brian says, look in antique furniture repair and cabinet-making books.
And for the record, correct working keys fitting individual warded locks are bit keys, but not ‘skeleton keys’. However, many cabinet locks had only 12 differs in a set, and need only a simple skeleton key (of the right size) to open them all. Common cabinet skeleton patterns are L, Hook, and Z.
