How challenging is it to mount the brass rondell?
It's quite a tricky business to do well (meaning dead flush & in exactly the right position). Many people think you just press them into the stem with a soldering gun. :rofl: Not so.
It
is true that GBD used a task-dedicated, electrically heated arbor press sort of machine that made short work of rondel placement, but that doesn't translate. Such machines move in only ONE direction, the stems were set in a padded V-block, etc. Trying to duplicate the results of a rigid industrial setup like that with hardware store hand tools isn't possible quality-wise, and has a high risk of trashing several hours of work. (The little medallion can only be added at the end)
Adding to all that is some of GBD's rondels were stamped from .8 mm thick plate, while others are almost foil thin. Just getting the latter sort off the old stem without damage takes some trickery, never mind what squashing it with the unequal pressure of a soldering iron's wedge-pointy tip would do.
The only way to get a guaranteed good & consistent result that I've found is to inlet the stem material by hand with a small rotary cutter, and glue it in place.
Is it from the original stem it do you have a stash?
My stash comes and goes. At the moment I'm only transferring them.