I bought them! Pics to follow.
Suffice to say, the set is old (in years) - the box looks like an antique piece. But the mics themselves are flawless, if cruddy. It's like they've never been used, there were absolutely no wear marks on the anvil or spindle faces of any of the mics. Spindle action is butter smooth. Not a scratch to be seen anywhere. Ratchets are all in working order.
The standards bars still have their protective resin glue caps on, as do the two larger mics. They have never been used at all. There is some very slight corrosion on the spindle of one of the mics where the protective oil failed, but other than that, WOW!!!!
The box still has its original sewed-up pouch of silica desiccant inside.
I am unable to find a date of manufacture, but there is a part number sticker: 103-913b and OMST-150.
As for the "corrosion" on the thimbles? It's a grotty muck from biodegradation of the foam pads. The foam inside the box is disintegrating, the slightest touch sends it crumbling.
I'm a happy chappy! I was concerned that the set would be SAE, but it's metric. Deal!!