Iver & Johnson info
They serialized their handguns from 1894 through 1946. Production for these stared in 1893 and Serial numbers for the Large frame .38 cal 1st Model beganm in 1894 with 00001 to100000 (Saftey Hammer model). In figuring your firearm out I would need any and all info on the gun. Patent dates, check for numbers on the butt, under the grips, trigger gaurds, etc. The writing on the braarel, especially patent date would be key. I'm not slamming Blue Book, their good, but W.E. Goforth worte a book cvalled Iver & Johnson Arms & Cycle Works Handungs 1871-1978.
Also check to see if you have a single post top latch, leaf spring and free wheeling cylinder.
By the by, serial numbers were not required on firearms in the US until 1968.