My oldest "mold of shame" is an RCBS .308-165 SIL (or however they name theirs).
I bought it super-cheap, used, from a forum member across the country.
Package got wet in transit. Mold cavities rusted a bit.
It's fine. It'll clean up. I just need to do it.
So, of course, the mold has been sitting here for almost 10 years, now, having never even been attached to a set of handles.
That, in itself, is highly ironic considering that I have several molds that were cut as nothing more than one-off experiments for very short term usage.
One of them, I think I only cast 30 usable bullets with, and that was enough to prove multiple theories that I was chasing. (Using hollow, tapered-base 'heavies' in .444 Marlin, without bulging the case body; and the ability for a Marlin 444 to feed and load wadcutters; and more. -- That mold used double-ended designs, with two different cavities. One mold, two cavities, four experiments.)
Learned what I needed. Now it's a paperweight.