Introduction
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.
The letter formats are: "A" (35mm), "B" (2-¼-square), "C" (3-¼-square), "D" (4x5), "E" (5x7) and "F" (8x10).
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. 
Quick Comparison
| Model | Mfg | Col. Type | Col. Height | Lens Focus | Focus Method | Max Negative Size | Price | Notes |
|---|---|---|---|---|---|---|---|---|
| C | 1938-1940 | Single Tube | 48 inches | Bellows | Manual | 3-¼ x 4-¼ (9x12cm) | Very similar to the D, and could share the same condenser set | |
| Super C | 1939-1940s | Dual-rail | Unknown | Bellows | Manual | 3-¼ x 4-¼ (9x12cm) | Big sister to the Super B; accepts a larger negative than subsequent C models. | |
| C-II | 1940-1940s | Single column | Unknown | Unknown | Manual | 3-¼ x 3-¼ (9x9cm) | Last C-series enlarger until the 1970s; accepts a larger negative than subsequent C models | |
| Super Chromega C Dichroic aka C67 | 1972-1980 | Double-Wall Girder | 45 inches | Unknown | Manual | 2-¼ x 2-3/4 (6x7cm) | MSRP: $499.50 (w/o lens) | Originally fitted with the dichroic lamphouse only; later the condensor lamphouse was fitted and the name changed to C67. Last color version had the C-700 dichroic lamphouse. Reviewed Modern Photography magazine, Sept 1973 (Vol 37. #9) |
| C-700 | 1979-present | Double-Wall Girder | 39 inches | Bellows | Manual | 2-¼ x 2-3/4 (6x7cm) | Condenser: $189.95; Dichro $369.95 | Only C-series still in production; recent models are fitted with the C760 color head |
| C760 | 1980-1989 | Double-Wall Girder | Unknown | Bellows | Manual | 2-¼ x 2-½ (6x7cm) | Condenser: $349.95, Dichro $499.95 | The most recent design, but out of production; many features (such as the lamphouse) are now fitted to the C-700 -- Reviewed Darkroom Photography magazine, Mar 1982 (Vol 4 #3) |
Series Comments
The C-series enlargers are very, very similar to the B-series, to the point where the differences between them blur. B-series enlargers are typically 2-¼" square, and C-series are larger (typically 2-¼" x 3-¼"), but there are examples of B-series machines that are larger than 2-¼" square. The C-series disappeared entirely for decades while the B-series ran, only to re-emerge in the 1970s as the B-series began to wane. Today the C-series is still in production whereas the B-series is retired.
That said, there is a lot of cross-pollinization between the two, to the extent that many (particularly later) models accepted each others' heads and condenser kits. So it's quite possible to find examples of hybrids, such a B-series chassis with a C-series color head.
Model Comments
Model C
.jpg)
This was truly a "bigger" enlarger, designed to take 3-¼ x 4-¼-inch negatives. It was the smaller sister to the
original model D, which took 4x5, and shared the same condenser set.
Minicam magazine had it in their "what's new" section:
The new Model C Omega for film up to 2¼" x 3¼" is especially built for the photographer who works in more than one miniature film size. Interchangeable dust-free negative carrier, double condenser assemblies and lens boards permit easy, rapid change-over from one film size to another.
The four foot steel post permits 8½ times linear enlargement for 2¼" x 3¼" negatives, 20 times for 35mm double frame. A 75 watt 110 volt GE projection bulb and highly efficient double condenser system permits short exposures on slower enlarging papers. An exclusive Dyna-Thermal venting system, together with the heavy bakelite lamphouse, keeps negatives cool.
Dust-free negative carriers are available in a variety of sizes; glass holders may also be obtained. There's a long focusing lever for speedy, accurate focusing.
Simmons lenses and Bausch and Lomb Tessars are available. The Omega is priced at $97.50. This includes detachable lens board, without lens.
Model Super C
The first of this series to look like a modern Omega; it had a dual rail column. Like the Super B , its big feature was a set of bellows both above and below the negative. The upper set could be used to adjust the negative stage relative to the light source, and thus eliminate the need for different condensors for different film formats.
Model C-II
A direct replacement for the original C, it was a less-featured version of the Super C. According to KHBPHotographix, it was the basis of the venerable DII/D2 models. This is the last of the C models until the series was revivied in the 1970s.
Model C67
The first of the revived C-series, it's a medium-format version of the D5.
.jpg)
C-700 and C760
The C-700 is the only medium format Omega machine still in production, and its dichroic color head is nearly identical to the one on the C760. The C760 has certain chassis upgrades, such as right and left-hand controls.
The C-700 ColorPrintmaker was a package outfit which included a rodenstock El-Omegar 50mm lens, 35mm neg carrier, ColorPrintmaker calculator, CP color filter set, easel and other darkroom accessories ($314.95)