Wiardgroup

Grant,
I offer the following simply as brainstorming / food for thought. No 
reply needed.

Perhaps you could scrawl something like "replaced mm/dd/yy" on the 
back of replacement panels (with one of those diamond-tipped etching pens).
... and/or ...
Put serial numbers and/or dates of manufacture on the back of panels.

Then, scratch in your autograph. :-)

John

P.S. Excellent post, Paul S.