[ithacaartist]

Kerosene, diesel fuel. or fuel oil make excellent penetrants for soaking something like this.

Also, a bit of physical shock/vibration after soaking may shift its spring to allow for a tiny bit of rotation of the lever. If you were to set it up on a towel folded up to be a good pad, then tap the shell with a rubber or soft-faced plastic hammer while putting a gentle strain on the lever in the direction you want it to go, it very well may shift the wound spring the tiny amount it seems to need. Just take care not to bend/dent stuff!

I'm going to give an old hard drive a similar treatment to see if I can get it to spin again, long enough to grab some old files from it. It "died" during a de-frag. It has never been given this treatment, and though a long shot, this 'defibrillation" (Clear!...Wham-o!) just might dislodge it.