Marlin Model 19 (Post office / R.R. gun?)

[SHOTARYE]

I have a Marlin Model #19 that my father gave to me, and before his passing on January 8th. of 2011 hew told me he thought this firearm could possibly have been a firearm that was once either a U.S. Postal Service or Railroad gun due to a second set of numbers marked on the barrel that are not the serial number. The firearm came from the LaSalle, county Illinois area so I would assume it would be that area's post office's or the old Rock Island RR line of that area. Does anyone have any advice as to how I could track down this information to see if this Marlin indeed is a USPS or RR gun. I can be contacted directly at email address ( kilkenny-south@msn.com ) if needed. Thank you.

[Regnier (gunrunner)]

Shotarye;

All exposed hammer, pump action Marlin shotguns made prior to 1921 had serial numbers on the barrel, and those numbers did not match the receiver serial number. If you look, there should be a letter next to the number, either an F, M, or a C for full choke, modified or cylinder bore or open choke.
It still may be possible that your shotgun was owned by one of the outfits mentioned, but doubtful that it can be proved. There are no records for the Model 19 Marlin shotgun, so there is no way of looking it up that way.
What is the barrel length of your Model 19? What is the letter next to the serial number on the barrel?