To say that the MCM/70 keyboard is unique would be an understatement. Because it supports APL out-of-the-box there are twenty plus keys that have special shifted characters like α and ∆. Not to mention that the more standard special character keys are in different places than on a modern keyboard. Plus I don't know if I've ever seen italicized letter key legends .

Believe it or not you can still purchase APL keycaps, like this set from UNICOMP (for a pretty reasonable $35).

While there appears to be a standard APL layout for the keys, the key legends look quite different. So I'm resigned to having to make my own keycaps. But how? 

After doing a bit of research I thought there were four potential options:

1. Waterslide Decals. Key legends are printed on special waterslide paper and transferred by first soaking them in water then sliding the clear top layer with the glyph and some adhesive to the keycap. 
2. Dye Sublimation. Key legends are printed (reversed) with special dye sublimation ink. The glyphs are then positioned directly on the keycap and transferred by applying heat (400 F - can be accomplished with a hair curler) and pressure. 
3. Laser Etching. While directly etching the legends onto a keycap has not worked very well, DIYers have had success by coating the keycap surface with print toner or dye sublimation ink then using laser etching to fuse the glyphs to the surface. Once done the excess toner or ink is washed away.
4. Purchase. A number of vendors will now allow you to submit SVG files with your keycap legends and produce the keys for you.  

These are arranged for the most part in easiest/cheapest to hardest/most expensive order. So my plan is to start at 1. and keep trying these methods in order until I get a result that I'm happy with. 

Regardless of the method that I use, I need to have the key legends defined. To that end I have used Inkscape to create SVG versions of the legends that can be scaled to fit the keycaps.  Here is what they look like.

Still needs a bit of work but a pretty good start.