[Rudolph31]

The original Super Lightweights had steel receivers and aluminum alloy trigger plates. Later they went to aluminum receivers as well.

While 1958 sounds reasonable for the year, I wouldn’t trust any tables for the Why? Series guns. A better way to date it would be to check out the Date Code on the barrel. Of course, if I understood your description properly it’s doubtful that your barrel is original.

Speed Load appeared on US guns in late 1953. I’m guessing they used up the remaining one piece carriers on the World Market guns. But 1958 is surprisingly late.

I had a Super Lightweight with an alloy receiver and no disassembly hole. The trick is to remove the Cartridge Stop and punch the pin out from there.

 

[Rudolph31]

The date code looks like (what I think is) Sigma, for 1959. Here’s the list:

 

[Rudolph31]

I don’t know what the B and M on the bottom of your barrel mean. I do know it’s not the date code, or the choke. Yours has a full choke, as indicated by the single * among the proof marks.

 

[Rudolph31]

As for reference material, there’s a ton of stuff, starting right here on the “stickies” on the top of this page.

Then go over to this forum and look at the stickies there:

Shotgun ID & Value

Find out what that shotgun is worth! Don't know what model it is...we'll help with that, too.

www.shotgunworld.com

Belgian Shotgun Identification Guide

Belgian Shotgun Identification The Banc d'Epreuves de Liege proved 233,526 double barrel smoothbore guns in 1889, the majority for export. In 1899 alone, the U.S. firms of Hartley & Graham and Simmons Hardware bought 90,000 shotguns, rifles, and handguns from Liege gunmakers. Most of the...

www.shotgunworld.com

Internet pages I have bookmarked include these:

Belgium

https://www.nramuseum.org/media/940941/serialization-date%20of%20manufacture.pdf

And, I certainly recommend the book soyknee mentioned.

 

[Rudolph31]

Looking over this post, I realize that you two are sick f**ks. Who needs more than one shotgun?