The plastic keys are actually a slightly different
size. All the
ones I've seen are beige plastic (but they may be slightly
later, mostly from Alphas).
For reference I have two DEC plastic keys here:
1217119-01 grey marked "'digital' and 'Anti Static'
1217606-0-0 blue marked "'digital' and 'REMOTE'
the keying part is just a single tooth on a 1cm cylinder.
The first is for BA213,BA215 cabinets (at least),
they work in pre-alpha uVIII's.
The blue key is for other purposes I don't know of yet.
John A.