I was taking apart an Osmia Piston filler, for a client who had bought the pen (on eBay I think), and wanted to get it restored. I found a most interesting "previous repair job", one of the strangest I've seen.
It looks to me, like someone used thread (yes, sewing thread), to try and make a new piston seal, when the other one degraded down. Take a look for yourself:
Here is the pen - with the piston removed.
So, here we can see the thread after I removed it, as well as some crusty bits of the original rubber seal.
My guess? I personally think that when the original rubber seal shrunk down, and got brittle (when it should have been replaced), someone who owned the pen decided to try and fix it by wrapping waxed thread around it.
Probably worked... For a few days. :)
Anyway, I just thought some of you might find that interesting! I sure did. Let me know if you've ever seen something like this before. Perhaps it's by design, and I just don't know it, but I'm pretty sure it's a home-job.
Wednesday I'll be showing how I made a new retaining pin for the piston knob! Fun. :)