I'm trying to learn some things about the US 49 Observation Telescopes - particularly the WW2 scopes. I believe there were 3 manufactures: 1) Bausch & Lomb Optical Company, Rochester NY, 2) Argus, and 3) Seiler Instrument Inc., St Louis MO. Is that correct?

The M49 appears to have serial numbers that continued into the Vietnam era. So I assume that each manufacturer did not have their own serial numbers or were given serial number blocks that allowed continuous serial numbers. Is that correct?

How many M49s were made in WW2 (i.e., what was the approximate highest serial number for WW2)?

Thanks.