Ancient mirror with interesting cell

[markse68]

I saw this in the Deutsches Museum last week and it shocked me- I thought the idea of using bearings as anti-astigmatism edge support  (with whiffletrees) was a new discovery but looking at the fascinating cell design of this c1794 metal mirror by Johann Hieronymus Schroeter it seems not! Strange arrangement though with both lateral and vertical wheels kinda cancelling though I guess if they can move laterally on their shafts 🤔 Difficult to take pics but there were three sets of these around periphery of the cell

[dobblob]

Just goes to show there is nothing new in this world.