I knew that producing an authentic looking keyboard for this project would be a challenge in two parts. First getting the physical keyboard layout right with the MCM/70 keys. The second challenge will be to obtain a keycap set with the special APL symbols (legends). Here is an MCM/70 keyboard.

Well I think I have the keyboard layout issue sorted.  After looking at many many keyboards online I found the following.

This is a keyboard for Ohio Scientific (OSI) computers that were popular in the mid to late 70s.  It's a very close match layout wise to the MCM/70. One small difference is that the OSI spacebar is only 8U compared to the MCM/70's 9U size. Also the MCM/70 has an ISO style Return (rotated L shaped) key, but if you remove and ignore the OSI's Repeat and Break keys and replace the Return key with the ISO model it's a practically perfect replacement.

So how does this help? Aren't OSI vintage keyboards just as hard to find as MCM/70 keyboards? Well yes and no. Yes originals are hard to find, but thanks to Dave from osiweb.org replacement keyboards are not. I used Dave's Sol-20 reproduction keyboard for my Sol-20 Reproduction and it worked out great.  If you check out Dave's Unified Retrocomputer Keyboard Project on GitHub you will see that he also offers keyboards for Apple I, Apple II/II+, Generic ADM/3A teletypes, and most importantly to me OSI computers. So I have ordered an OSI keyboard PCB and stabilizer, OSI keycaps, and an encoder. 

As for the MCM/70 APL keycaps, well I'm still looking into that. Lots of options. More later.