1941 Model 11 Sportsman 28 Gauge?

[Notanexpert]

I have a Model 11 Sportsman 28 g in my possession. The serial number is 1055929 and there is a 20 stamped on the inside of the wood forearm. It seems obvious that this was a 20 g stock at some point. Here’s where I need folks who know way more than me: The barrel is a true 28 g barrel, fitted perfectly. Vented rib with solid posts. The only thing stamped on the barrel is “28 GA 2 3/4 Shell” underneath the barrel is stamped “Sept 41” and 3 digit number of “109”. It seems like this barrel was made in Sept 1941, which falls in the time period of the serial number of the gun.
1. Could this gun have been a prototype that got paused because of the war?
2. Could this gun have been a boutique modification? If so why didn’t the modifier put any of their markings on the barrel?
3. Could this gun have been made by an Remington employee as a personal gun?

The gun fits together perfectly, shoots and cycles flawlessly. The bluing on the barrel matches the gun. I have had it in my possession for almost 40 years. It was acquired in an lauction that had a matching 410.

This gun has always been a great mystery and conversation piece. Looking forward to hearing other ideas from knowledgeable people.