The three Simmon brothers began producing enlargers in the mid-30s and are still in business today (as OmegaSatter). The original company was Simmon Brothers, and the greek Ω symbol was the logo; but over the years the symbol became the name of the product. Enlargers by Simmon Brothers are almost always referred to as "Omega" enlargers.
Omega enlargers typically follow a reliable name scheme: the letter designates the format size of the enlarger (i.e. the largest negative the enlarger can accept); the following number indiciates the model generation. A "B" size enlarger is larger than an "A", a "D" is larger than both, etc. Typically the higher the number, the more recent the model. E.g. a B-22 is more recent than a B-3.
There are some exceptions as noted. Marketing departments love to depart from a standard naming scheme, and in some cases a very popular model enlarger (such as the D2) remained in production after more recent machines were discontinued.
To the best of my knowledge, the XL designation refers to an extended-length column.
I have a few of Instruction Manuals and brochures available for download.
|Model||Mfg||Col. Type||Max Size||Lens Focus||Notes|
|Complete (Model A)||1938-1940s||Single Tube||35mm||Bellows||A self-contained unit. Sister to the Model B|
|Complete (Model B)||1955-1962||U-tube||2-¼"-square (6x6cm)||Bellows||A self-contained unit. Sister to the Model A|
|F||1965-1973||Quad-rail||8x10||Bellows||Huge machine meant for professional and commerical work.|
This is the catch-all group for anything that didn't quite fit elsewhere.
Complete (Models A and B)This is actually the same enlarger, simply offered in two different sizes: the A size was for 35mm and the B size for 2-¼"-square. It was a nifty idea: it was self-contained in a box that provided its own structure. The front dropped down to become the baseboard, and the head swung out from the top; so that the whole thing could be quickly and easily packed away for storage.
This 8x10 model followed the series letter progression; but since there's only one, it was simply the F.