I recently scanned this photo from an old lantern slide:
It shows a man standing with the mirror cell for the 200-inch telescope at Palomar. Unfortunately I do not know who is in the photo. Fortunately there is a date given on the photo: 10-25-35. October 25, 1935.
The photo was later featured in an ad for Babcock & Wilcox, the company that built the mirror cell.
The ad ran in the 1948 Caltech yearbook, The Big T.
It seemed like a good time to run this as all the openings in the mirror cell contain the mirror supports which are currently being serviced. In the ad the photo on the right shows optician Marcus Brown climbing the backside of the mirror. A portion of the mirror supports can be seen sticking out of that side of the mirror.