If it helps your sale in any way, I bought a set of these in the summer for around £50 posted:http://www.retrobike.co.uk/forum/viewto ... 0#p1972620
This is the third pair of these I've seen floating around over the years - of course, your's might be the second one simply doing the rounds!
They definitely aren't Bontrager or Tange S/Bs, and are a fair bit heavier than both.
The general consensus is that they're an asian knock-off, but I'm not suggesting that for certain.
[Certainly, the steerer on mine is [I think from memory] of Italian origin, so not sure if that adds anything to the mix...
Maybe an Italian knock-off?!
I purchased mine as a quick stand-in for something else so wasn't too fussed about integrity, but for some simple guidance I'm attaching a couple of pics of one type of Bonty crown, and one type of SB crown - note how the crown on yours is a mix of the haunch on the Bonty, and the arched underside of the SB. Aslo, the crown on yours is reduced in thickness and follows the form of the steerer.
Hope this helps a little - probably not!