What year was an Iver Johnson 5-shot 38 with no serial number and a letter logo on the right side of the hammerless cocking slide made?

The serial number is hidden on the frame under the grip. Removal of the grips will expose the s/n of you gun,then it can be dated. A great source of information on Iver Johnson firearms is The book "Iver-Johnson Arms & Cycle Works Firearms 1871-1993" by W. Goforth