I googled removing rubber stamping from plastic and found a Model Railroad article describing several methods. I applied 91% isopropyl alcohol over lettering with a q-tip, waited 5 minutes, repeat several times, then gently scraped off with new Xacto flat blade. Reapplied alcohol and a 5 minute wait after each scraping until lettering is gone. Don't try to get everything in first application, took me three rounds to get it all off.
Only downside is it leaves surface scrape marks, but for my purpose no one will see the crane close up and if someone should remark, I would say lettering was sandblasted off sheet metal by new owner (always have a backstory!). And after weathering, it won't be that noticeable.
