I just joined this community through the link from cave-astrola.com. Thought I'd register the mirror on my 1974 Model D Transportable.
Mirror size 12.5"
Serial number is M749686
74 3/16" focal length
Dated Oct 3, 1974
Writing is cursive
I took some pictures in 2014 when I had it re-finished. Not very good, but it does validate the mirror. I'll try again next time I have the mirror out. Also attached one of the scope and a perhaps interesting one of initials and date on the worm wheel mount housing. Dated 9-74 on a 10-3-74 scope suggests it's a Cave employee.
Thanks for the archive recording.
I tried to get my file sizes to total less than 500KB, but not successful. I hope you don't mind 2 added postings