If you want to keep the decals, I would advise proceeding with caution. I salvaged a 40s Underwood Universal from a shed last year. It pretty much looked like a 'goner'... caked in dirt, stuck keys, no ribbon, feet missing. A big, beautiful moth crawled out of the housing when I brought it inside and started hitting the keys (said moth was set free again outside). Anyways I spent alot of time servicing the machine, replacing the ribbon, finding new feet. I must have spent a good eight hours with rags and Qtips cleaning it up. The colour of the housing turned from brown to grey. I was kind of stuck when I got to cleaning around the decals. They were detailed and complex to clean around -- I started with a wet Qtip but the front decal started to disintegrate quickly around the edges. I wanted the housing colour to be consistent ie. I didn't want to leave a brown 'cloud' around the decals, so I made a decision to clean away and sacrifice the front decal (before I started cleaning I took some closeup photos 'for the record'). The decal left a bit of a 'ghost', but otherwise I think I did the right thing for THIS machine, in the end. The typewriter ended up looking quite presentable, and I have left it on display. If the machine had much collectable value I think I would have preserved the decal; actually I don't think I would have done any heavy cleaning at all. So my advice would be to consider the machine (make, model and vintage) and make a conscious decision to either be content with it 'as is', or be willing to accept that any alteration you make to the machine may affect its value or aesthetics. Now, having provided that long story, I'll mention that I did see somewhere (while surfing the typosphere) that someone had a number of replica decals for sale, but as I recall they were limited to 2 or 3 models. But that leaves open the possibility that others might be found.......

Does anyone know what decals from the 20s and 30s are actually made of? I've tried Googling, with no success so far.

Also, I'd assumed that all old typers had a layer of paint, then the decal, then a layer of varnish; the latter providing protection for the decal. Is that right?