Tom,
The only way I can back it up is by photos, both oblique, vertical aerials and ground level shots, and also by going out and looking at the stuff and seeing what once existed in the ground. I don't think it's much different then you or Jim do when you look at courses and utilize a golf club's historical information and archives.
Also, without going back and looking at the previous post (I haven't seen this thread since it started some months ago) I do remember seeing that aerial and going--That's Billy Bell bunkering. You may have proof to disprove this, but if it isn't Bell overseeing it, then certainly its someone that built them for him.
As far as Bell vs Watson or Watson vs. Bell, I'm playing no partiality and for what it's worth, I hvae identifeid a few courses now that were incorrectly identified as Billy Bell, when in fact they were Willie Watson. I can provide you with that information if needed, but not on-line.
There are several clubs I have done an inordinate amount of research that feature courses that claimed William P. Bell was the original architect. Both of those instances the research proved that wrong, and further evidence of photos, both oblique, vertical and ground level show bunkering not even close to the same or anything remotely like the dramatic aerial showing Belvedere.
As far as revisionism, I don't think I've done anything that could warrant that accusation, In fact I detest the thought of revisionism, but maybe you know something and aren't actually coming out and saying?
I don't think I've ever make a claim that I wouldn't be able to back-up, but what I've seen of Belvedere--that particular aerial, well it looks very Bell-like. Could you provide some evidence which claims it isn't? If you can, please do, it will be definitive information on a style that was never seen in any Watson courses out here.
I could also go on further but will not simply because if Mark wants 411, he is going to have to call and ask for it.