I didn’t expect it either. One of their advisements, that has been put on line, gives the specs, including the tubing manufacturer. I forget who made the tubing. I wonder if ther is any info on the tubing factory?
When I saw that advert you posted on the other thread stating 22lb for an all steel bike total weight my eyes lit up.... aluminium was around then but it was twice the price of gold and more rare!
Ive been scratching my head since quite a bit too!
I've also googled that tubing with no luck either

I'd get all the other stuff on the other thread on to this one chap....this is a special bike you have.....
That tubing is very clever and wouldn't of been cheap to buy or to tool up to produce! I know bicycle's were a huge booming business back then but that tubing really is something else surely it was used in other products....part of me says aviation.....but .....the Wright brothers hadn't even got off the ground then....that was 10 years later!