Coaly - I took a closer look at that corner of rear and indeed it is stamped "4033". I thought the "FP" on the underside was for Factoryville, PA maybe. Just thought I'd get back to you on that number.Thanks for the detailed info on your stove. I've been trying to figure out the FP 4-33 on the bottom. Never saw welders initials on the bottom of a PA stove, and never saw one with a dash in the middle of a number. Unless since it's easier to weld a line than a zero, it could be the builders initials and stove number 4033 ?
I bought one in Jersey stamped on the top left rear (looking at it from the back) with a NJ serial number. I don't know of a NJ fabricator, only NY and PA, so that didn't make sense. To further complicate that one, the weld on the bottom looked like a NN 77. Could be a NY, made in NY for a Jersey distributer / retailer who stamped the serial number on the back. I keep track of what is found in hopes of deciphering it all some day.
View attachment 84153 Same stove bottom; View attachment 84154
Added a pic of the hot Papa in action for my avatar. Hope you enjoy. Thanks for your help and Happy Holidays!