Regarding the cradle brackets/latches:
I took some pics of the bracket latches on the #40 Queen Anne cabinet that came with the Singer 301 I'm keeping. Here's one side (no part number on this latch.)
[ATTACH=CONFIG]531832[/ATTACH]
Here's the other latch with Simanco part #136413:
[ATTACH=CONFIG]531833[/ATTACH]
Here's the underside view for those of you (us?) looking to duplicate these in your metal shop!
[ATTACH=CONFIG]531834[/ATTACH]
Finally, here's the business end, as viewed from above. I can only assume that the cork that supports the machine is original...it looks pretty good for a tiny piece of cork that's been (at least occasionally) supporting half the weight of a 301 SM for 63 years!
[ATTACH=CONFIG]531835[/ATTACH]
Brian