What is this Starrett item?

[ARC-170]

I found this pair of "wedges" with some radius gauges, but they don't seem to go together. What are these? The box they were in states that they are adjustable parallels, item #154A, but when I looked them up, that was a different looking item. I'm thinking the box wasn't the proper one. These do have "The LS Starret Co. Athol Mass USA" engraved on them, so it's some sort of Starret item. These look like some accessory part to something, but I wasn't able to find anything obvious when I was looking a the Starrett website. Any idea what these are?

 

[tjb]

Not sure what the top two are, but the one on the bottom is a ruler.

 

[macd55]

Your Starret scale fits into the slot and clamp on and you can scribe a staight line on a small diameter piece of stock or you can hang it over the edge of a plate and use it as a staight edge. I have some and in 45 years of working in machine shops I might have used them a couple of times. They are in the Starret catalog.

 

[SLK001]

Yeah, they are scale (rulers) clamps.

 

[benmychree]

Keyseat rule clamps.

 

[ARC-170]

Thanks for your help!

These are Starrett #298 key seat clamps. Here is an image showing how they are used:

They retail for $70-$100 new, but are for sale on Ebay for about $20.

 

[master of none]

I'm glad you ask that question cause I'v had two hanging around for years and didn't know what they were, thanks for asking.