Stanley 200 honing guide

We were passing by an estate sale the other day and stopped to take a look.  The guy was a hoarder and there were boxes of junk scattered around the yard.  Something caught my eye and, when I picked it up, it appeared to be a vintage Stanley honing guide, though I had never heard of it.  I took it to the seller, offered him $5 for it and he asked me what it was.  I told him what I thought and he immediately went on Ebay and found one for $110.   I am sure I could have bought the entire box for $5 and, of course, I didn't have to tell him what it was, but that's me.  Obviously irritated, I put it back and he promptly told me he would take $5 for it.

So, here is what it looks like after I cleaned it up:

It's got some light pitting on the roller that doesn't affect use.  You can alter the angle of the blade either by varying how far it protrudes from the guide or turning the acme-threaded rod on the roller.  One of the things that intrigued me about it is that it is long enough to let you have the roller off the sharpening medium.  I like this idea because I use diamond paste and it keeps the roller from being contaminated:

I sort of assumed it wouldn't work very well because you don't read about them and, so far as I was aware, there is only a cheap modern version that is anything like it.  However, I tried it out on this plane blade and it worked really well.  I've got the roller a little low in the picture, but there is a lot of flexibility in how you adjust it.  I wasn't sure how well the thumbscrews would work, but they held the blade securely.

Now I'm wondering why a guide like this seems to have fallen out of use.  I did some research and it appears that it wasn't popular because the sharpening medium has to be a uniform thickness or the angle will change.  That isn't a problem with diamond stones, plates and paste or sandpaper but it was a problem with oilstones.  Some woodworkers seem to really like them.  I think it is a keeper.

Here is an interesting video by a luthier who has developed a similar guide that he uses with waterstones.  One of the advantages he claims is that it keeps him from gouging a very soft 8000 grit waterstone he uses.  The way he uses it to polish the back is interesting too.