Steel ring 500 increment markings

[davidicusrex]

This is a heavy steel ring about 18” diameter. The inner and outer rings are marked from 0 to 499. There are two small indicators that can slide along the inner and outer rings. The two heavier tabs do not move. There seems to be a race or groove between the two rings along which something can move. It weighs 45 lbs. i found it in a barn filled with antiques about 50 years ago. Thanks for your interest.

 

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[Jose The Goon]

Very interesting find. So far, no one seems to know for sure what this is, & neither do I,
but I will speculate a bit. It seems to be a large, hefty gauge of some sort.
It could possibly be some kind of adjustment ring to a very large piece of machinery or maybe some kind of adjustment ring to a very large sophisticated camera or telescope. Notice the different rings on this small 35mm camera that adjusts the depth of field scale, aperture ring, distance scale, & focusing ring.

Parts of The 35mm SLR Camera

Battery Cover - This is where the battery is stored. Depth of field Scale – Tells you the depth or amount of space that will be in focus. Distance Scale – Tells you at what distance point the...

gomezwithart.weebly.com

I know your concentric ring thing is not exactly like the camera, but yours could be
something similar in function for some larger, man-made precision item.
Most definitely a very cool find & I'm sure the precision engineering & quality of the item has a lot of work & brain power behind its' creation.
CONGRATS on a very cool find !! I hope you get to the bottom of the mystery. CHEERS !!

 

[Back-of-the-boat]

I would think it has something to do with a metal lathe.

 

[Digger RJ]

This is a heavy steel ring about 18” diameter. The inner and outer rings are marked from 0 to 499. There are two small indicators that can slide along the inner and outer rings. The two heavier tabs do not move. There seems to be a race or groove between the two rings along which something can move. It weighs 45 lbs. i found it in a barn filled with antiques about 50 years ago. Thanks for your interest.

Nice!!! Congrats!!! I agree with
Back-of-the-boat .