Help Identify this Caliper

[Cleave]

Here's an old outside spring caliper to identify the maker. All my others have two separate legs, a pivot pin, and a spring. This one is one forged piece plus the screw and nut. Pretty cool. This one I suppose the spring is a little bit tweaked since I can't close it under about 1/2" and can't open beyond about 2".
There's a maker's mark on it, looks like R&L Einstein, and below something ends in ****DLER.
Any ideas who made this, when, and where?

 

[RTM]

Nothing turning up in DAT on those combinations.

 

[Cleave]

Is that directory of american tools and machinery patents? I could be misspelling something as well.

 

[four.cycle]

try rubbing some chalk into that stamping and see if you can get a clearer resolution. I can't make heads or tails of it. the serifed font is making me wonder if it's perhaps British.

 

[Oregon Dave]

Boker made this style; but usually stamped their name on the opposite leg.

 

[RTM]

Is that directory of american tools and machinery patents? I could be misspelling something as well.

No, DAT is not DATAMP.

Directory of American Toolmakers (pre 1900).

https://www.amazon.com/Directory-American-Toolmakers-CD-ROM/dp/0943196051?tag=atomicindus08-20

 

[Cleave]

Boker made this style; but usually stamped their name on the opposite leg.

Interesting. Same style as Boker who I think was originally German, with probable German name (Einstein) stamped in English.
Maybe old Albert made this in his garage...

The legs on mine are a bit thinner than the Bokers.

H. BOKER Calipers in 3 3/4 and 4 1/4 inch Sizes EXTRA FINE - 78405

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www.jimbodetools.com