[rescue] How to open a TK50Z-GA?

[Mouse]

I've got a DEC TK50Z-GA which appears to be broken.  I offered it FTGH
here on 2021-09-21 and heard nothing in response.  So I infer nobody's
interested - which is hardly surprising.

So I wanted to open it up and remove the TK50, turning it into a
relatively generic SCSI enclosure.  (It's a lunchbox-sized DEC SCSI
enclosure with a TK50 in it, obviously with brige electronics, with two
Centronics connectors for SCSI and a three-bit DIP switch for SCSI ID.)

But I can't figure out how to open it.  The top and sides are a piece
of relatively heavy sheet metal, wrapped around and fastened onto the
bottom with four screws.  But, upon removing those screws, the metal
still won't go anywhere; the front and back plastic pieces extend out
about to the outside surface of that metal, so it can't slide forward
or backward.  I could just pull the sides apart, bend the metal enough
to lift it up.  But the metal is heavy enough I suspect that would
surpass its elastic limit (as in, it wouldn't spring back into shape
afterwards).  That wouldn't necessarily be a problem - I could still
fasten it on with the screws - but I can't help feeling there has to be
a better approach, largely because (if I'm right about the elastic
limit of the metal) that obviously isn't what was done during
manufacture or the metal would have sprung outwards as soon as I took
out the screws.

There are ten other screws visible on the bottom (four holding on the
feet, four holding what I suspect is the power supply to the base, and
two holding on a small coverplate that reveals nothing of interest -
just part of the TK50 proper - when removed.

Any hints?

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