If all else fails and if someone would like to spend 5000 hours, 5 years, and be subjected to a lot of guff, one might try this:
1) compile a database of all known Ingrams by serial number - determine if the SN's are consecutive. I think to have an adequate graph you'd only need 50 or so guns, maybe less.
You're kidding, right? The books and serial number lists compiled on the Syracuse Lefever guns documented a whole lot more than 50 guns, and there is still much confusion, and incorrect assertions concerning them. I could well imagine that such careless and inadequate research might lead one to being subjected to "a lot of guff".
I suppose it could even permit one to conclude that Ingram had over 300 employees, with no real evidence. It helps to use plenty of conjecture, and terms like "might have", "perhaps", "could have", and etc. a whole lot.
