A lot of breakers back in the day were not 100%. I remember the commonplace "frame with V5" on eBay for sale at about twice the price of a new frame from the manufacturer. I think the likes of Datatag and so on really began the decline of that, but probably the engineering improvements that made secondhand parts much less profitable. Breakers had the problem everyone wanted the bits that you broke in a crash and all the bikes people wanted to sell had been crashed.
Some scrote stole my XL250 and Norwich Union gave me virtually nothing for it as it was old. They fetch 3 grand now. Humph. I bet it died going round and round a field somewhere with a halfwit riding it. I had just got my GPz 750 back after it too got pinched (living in London then). The Kawa had done 7 miles or so and in that time they had bent the forks somehow. They got caught and a slapped wrist. The "victim support" people contacted me and I asked for the details of the thieves so I could sue them for the uninsured loss (car hire and so on) but no reply. Not much "support".
I guess trials bikes are not worth enough to be a major issue, particulalry when you look at new sports bikes. Top end Ducati now 13 grand plus and a grand a year service costs. Phew. I will stick with my old Suzuki.