The magic wooden prop.
Ah, that's interesting... I've heard of this practice of hammering a close-fitting hardwood 'plug' into the bottom half of the steerer-tube, but I've never actually seen one in real life. I can just about count the bikes that have passed through my hands over forty years on the fingers of one hand, so my 'sample' is a bit small. I was never curious enough to enlarge it by sticking a little finger up random steerer-tubes on bikes parked in the street!
In my ignorance, I suspect this practice to be more common in mainland Europe than in the UK. OTOH, it's equally possible that I am the only foolhardy two-wheeler who hasn't got this hardwood plug up their steerer-tube.... I've never seen one on Retrobike before, either.. not that I've scoured every thread, looking for one, but you'd expect to find one mentioned somewhere?
My theory, based mainly on ignorance, is that this plug is security in the advent of a failure of the steerer-tube/fork-crown junction. I'd guess that brazing a steerer-tube into a big fork-crown casting might need a bit more heat than brazing frame-tubes into lugs, which might make the steerer a bit brittle.... plus you have the unavoidable 'step' between the crown-race seat and the steerer-tube- another 'weakness', and of course, unlike the frame, there is no 'triangulation' in the forks to keep things together... So, god forbid your steerer-tube gives up its integrity at any speed, but if it does, that hardwood plug hopefully keeps things functional enough to stop your bike in something like the usual gentle fashion, rather than the ultimate emergency-stop of burying the bottom of your head-tube in the tarmac.
How often do you come across these hardwood plugs, Gastheerg? Sometimes? Always? Nearly always? or Hardly ever? Same question to anyone else- mainland Europe or UK- I'm interested as to how common this practice was, or is...