David -- you prompted me to search for keys on Amazon -- I might order this one:

https://www.amazon.com/dp/B0BS1CMC3Q/ref=sspa_dk_detail_2?psc=1&pd_rd_i=B0BS1CMC3Q&pd_rd_w=9Dy8g&content-id=amzn1.sym.eb7c1ac5-7c51-4df5-ba34-ca810f1f119a&pf_rd_p=eb7c1ac5-7c51-4df5-ba34-ca810f1f119a&pf_rd_r=9HAPHTDP79A1PKMGVNE3&pd_rd_wg=tXRfS&pd_rd_r=7663be78-a387-4f16-8ae0-2a279a800577&s=electronics&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

If that back plate that the height adjustment screw rests on is electrically neutral, then it forms a NC switch for muting a speaker or even operating an antenna relay.

73, Jeff KH6O