I have just now stumbled onto your excellent post. I'm probably way too late for your needs but I have a 16B-6 I can posts pictures of if your still need them.

OK. give me a couple of days.

I know that manufacturers of guitar pickups dip their windings in some sort of wax. Beyond that, I have no idea. I do know that bee's wax has a high melting point. So it might work for an electronic dip. Don't know if it would contain or stop any stray voltage. But liquid bee's wax would flow into every crack and crevice.

Here is something I found on making guitar pickups. Will it apply to making transformers? I don't know, but this might give some useful info.

https://www.instructables.com/id/Make-A-Guitar-Pickup/

Potting or saturating a pickup with wax is done to help keep the wires in the coil in place and prevent the pickup from becoming microphonic.

I used Gulf Wax (candle wax) to saturate my pickup because it was available, but you could also use a mixture of 80% candle wax and 20% beeswax.

Melting the wax directly on top of a heat source, in a saucepan on the stove, for example, can overheat the wax and cause it to become highly flammable. And we do not want to lose our eyebrows while making guitar pickups do we? NO! So, to melt the wax, I filled a big container about half full of almost boiling water and placed a smaller container inside. A tin can works transfers the heat from the water to the wax more effectively, so use one if you have one handy. Gulf wax comes in blocks, which don't melt very quickly, so I used a knife to break the wax into smaller pieces. Then I put this wax in the smaller container.

When the wax is completely melted, hold your pickup by the lead wires and submerse it in the wax. You will see bubbles coming out of the coil and you need to leave the pickup in the wax until the bubbles stop. For me this seemed to be about 5-10 minutes, but for you it could be longer.

Take the pickup out of the wax and wipe of the excess while it's still in a liquid form.

I think the factory used rubber stamps and not stencils to ID these. I check into getting a rubber stamp made and was quoted around $15.00 which is not bad for a rubber stamp. But the ink was killer priced. I'm still thinking on it.

The pic is not of mine but I do have transformer marked with the manufacturer name stamped on like the one you see here. The maker was Ravenswood Electronics in a town called Ravenswood near/in near Chicago. The Chicago pinsiders might be able to shed light on the town of Ravenswood.

Anyway, the transformer in this pic plus one I have are the only two I have seen with the Ravenswood name stamped on. I have no idea how many were tattooed like this. When I get around to marking mine I will probably include the name along with the number.

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I did like the OP and wire brushed the surface and painted them black. I have not had any problems (that I know of). Are your saying we have to strip the paint off and do the gun blue thing?

Your numbers look OK. I can see the small difference in the letters. A lot of collective wisdom here may turn up the correct font.

My question is since you are tooling up for a vinyl stencil are you going to be having big black holes in the center of your 6 and 0's? Or is this a stencil with adhesive backing your stick on like Pinball Pimp stencils for a one use only item?