There weren't really many commercial transmitters in the 1930s as most hams built their own.   But many of the ones that were offered came from the transformer companies who had two chances to profit.   First, from those who would buy the kit, and two, from those would would see it in the (free) booklets the companies provided to their distributors who would then sell the iron to hams who would build a copy from scratch.  Back then, there were no "old TV set transformers" that many of use grew up having access to so just about anyone building a homebrew transmitter had to buy high voltage transformers, heavy duty chokes, modulation and mic input transformers, etc.     Only the smallest rigs that might used a power transformer from a broadcast radio but most of them were repaired rather than scrapped.   

Two prominent transformer manufacturers,  Thordarson and Stancor, took this approach.   Today it is called a "reference design", and back then it served to not only show hams how their transformers could be used,  but by showing a range of power levels the companies could highlight the breadth of their line and offer suggested transformer and tube combinations for home builders.

The Stancor 10P is the "runt of the litter" when it comes to these reference designs.   A common 10 watt MOPA with a 6J5 oscillator and the very popular 6L6 as power amplifier.  Another 6L6 served as the total modulator, with a carbon mic transformer eliminating the need for a speech amplifier stage.   A model 80 rectifier rounded out the four tube set.   

A plate modulator in a 20 watt input rig is a bit unusual.   Leo Meyerson at WRL would go with Heising modulation on all the Globe Scouts a decade later because it was cheaper to buy a choke than a full modulation transformer.   Later entry-level rigs from Heathkit,  Lafayette,  Ameco,  Knight-Kit etc. used screen modulation which was cheapest of all to do.  CW-only rigs could be retrofitted with screen modulators from EF Johnson or WRL and some even built cathode modulators that plugged into the key jack!.    The neat thing about the 10P is, with a carbon mic transformer that has a very high step-up ratio, it was possible to make 5-10 watts of audio with a single 6L6 - a one-tube modulator.   And the carbon mic's response peak in the speech range provided natural "audio processing".     With it's four pieces of Stancor iron the 10P weighs in at 14 pounds in a package less that 1/2 cubic feet in size.

I'd had my eye out for one of these very cute transmitters for some time but never came across one til the Winterfest hamfest in St. Louis in January 2024.   It was cosmetically challenged with rubbed-out paint and no lettering on the panel, but the seller said the SK who restored it had done a good job, including a few beneficial mods such as a 3 wire line cord and fuse, and adding voltage regulation of the oscillator stage.   Stancor did a clever thing - by using a key jack with a set of isolated SPST contacts the modulator is disabled whenever a key is plugged-in.  Removing the key shorts the cathodes to ground for phone operation.   The only tuned circuit is the PA tank so while the 10P can probably work on most ham bands by doubling - it probably works on more than one at a time!   An antenna tuner should be used with rigs like this to further attenuate harmonics.   

I felt I had the tools and know-how to restore it to the original appearance.   Fortunately no prior owner had given it a severl "Black and Decker treatment" and while dull, the original paint wrinkle finish was still visible.    A light overspray of Krylon satin black for the cabinet and smoke gray for the panel was all it took to bring them back to a nice look.   I'd found a photo of a very nice original 10P from WØVLZ's excellent blog site, but decided to change up the color combination a bit.  I think the result looks as good as the original.

Part of the reason was to maximize the contrast of the lettering on the new panel escutcheon I was planning to make.   I started by sanding the original aluminum piece down to shiny bare metal and then applying two coats of gloss black.   I'd recently acquired an Elegoo Phecda 20 watt diode laser engraver which I knew would do a good job of creating the panel.   This  type of laser isn't able to engrave metal but it can remove coatings like paint or anodize from metal surfaces, creating a high contrast by exposing the shiny metal underneath.    It took a few iterations over the course of 2 or 3 days to get the artwork right, using Lightburn software and eyeball-copying the design I'd found online.   Tests were made by reducing the laser power settings and engraving the desired pattern on posterboard.   Once I was satisified with the result,  the blank panel was carefully positioned and etched.   The process took about 45 minutes with the settings I chose and given the nature of the design.  Since small particles of paint are blasted loose I turned on the air assist pump to blow these out of the laser nozzle area and also to keep them from being redeposited on the surface.    The photos below show the result even though it's difficult to get good photos of laser engraved metal due to reflections. 

I'm not a perfectionist but I think it came out pretty good.  The re-assembled transmitter now looks as good as it works with 10 watts resting carrier on AM phone and a bit more on CW.