Looks like most of the questions have been answered. That snap ring retainer was a great idea on paper and a total failure in the field.
They are rarely found today as most of them were converted to a set screw, just like Lyman did.
The 55 passed into history in 2019 after 120 years of faithful service, replaced by something easier to produce (cheaper).
Gone, but not forgotten. Progress is not always an improvement.
The old style 55's had a spring steel clip that held the funnel / drop tube.
On this one, there was a small amount of loose fit.
Each time I would fit a case in the end of the drop tube and drop a charge , I could feel " a bit of wiggle ". I didn't like that............
I decided to remove the clip and drill and tap a 10-24 threaded hole and install a set screw. No loose fit now. Solid as a rock.
Seems from reading about the old Lyman 55's that I'm not the only one to do this modification. Very common.
At some point in the past, Lyman abandoned the idea of the spring steel clip / spring to hold the drop tube instead going to a threaded screw.
~Four years ago I dropped my ca. 1982 #55 pm,, snapping off the handle. I telephoned Lyman, which had no replacement parts, but did offer to sell me a new one for $60 shipped. (That price was significantly lower than used #55's I saw on line.) When it arrived, I noticed the adjustment bars, etc. weren't as nicely fitted as my original/broken one. Ergo, I swapped them out and they fit perfectly. As for versatility, it may not be a Harrell, but it is very accurate with everything from Bullseye and Clays to IMR 4350. (It does an especially good job with WC 860.) It takes a bit of fiddling to accurately measure a new load or propellant, but that's what a scale and notebook are for. Lastly, with finer powders like Bullseye, it's a good idea to take the innards out, clean out the powder residue, and re-lube with graphite.