It's called a Known Ranger. Made to make quick adjustments between ranges. I have one in the original box. If I can figure out how to post pictures, I'll put some up.

Thanks guys.  I knew you would know.  wcf3840- if you have the instructions in your box, I would love to see them.
Phil

Also can also found in the Lyman 1940 Gun Sights No. 27 Catalog.

The name?  When Lyman introduced this gadget, The Lone Ranger radio series had been for several years one of the hottest shows on the air, & by '38, movie serials were also in production, followed by one of the very earliest TV series.  My family was a long time getting a TV (the nearest TV station was 50 miles away, so a huge antenna was needed to pick up anything), but the radio show was still running into the early '50s, so I remember hearing the  unforgettable introduction to the show:

"Return with us now to those thrilling days of yesteryear, when from out of the past come the thundering hoofbeats of the great horse Silver! The Lone Ranger rides again!"

In reading the description about how this tool works I still don't understand how it saves wear on the adjustment knobs. Wouldn't they still have to be turned?

bohemianway wrote on Nov 19^th, 2018 at 3:33pm:

  You would only need 10 revolutions to go from 100yds to 1000yds.
I don't know if they have that much adjustment.

If having an understanding of the scope settings and how to read them and then having taken the time to note them it's really about the same with or without the device.