Digging around a bit more, the Reynolds sticker is one used in the 1930's, so mid-late '30's will be about right (531 didn't come in until 1935).
Can't see anything stamped ont he cranks, but then again they are a mess of razor sharp chrome flakes, so that is no surprise.
I have rescued the hubs, which are now soaking in white spirit to get all the muck off before stripping them down to clean and re-grease.
The rims are a write-off, though as they are steel tubs rims and in the same state as the cranks, i.e. rusty and flaky. They are 26 * 1 1/4 (597) so, ideally, for safety's sake I will be able to replace them with 650A (590) rims in alloy (if I can find any 40 hole ones).
The headset, and other bearings, move freely so that makes the whole strip down a lot easier (or it did until I managed to bend one of the cotter pins whilst trying to knock it out!
Hopefully I will have the whole thing in pieces by the weekend (man-flu permitting) and then the rubbing down and cleaning ready for paint can begin (and hopefully I can get decent photos of the paintwork so I can get it replicated). The rusty bits that I had time to rub down yesterday came up nicely, going back to solid metal very easily, so deffo just surface rust, phew!
The saddest thing is that the lovely, white, Blumels that would have been fitted as new were ripped to pieces so they were the first thing that went in the bin.
2009 Ridley Triton-T, full Ultegra
2011 On-One In-bred 29er Monster Cross
POS fixie, based on a Unknown steel frame.