We have a lot of 2 socket screw calculator charts, a bit larger than pocket size.  The green one is a  hand held slide socket screw chart by "The Allen Manufacturing Company".  It measures about 6 5/8" x 3".  As seen in my photo you slide the inside card to the correct  diameter and it adjusts all the other dimensions on the card...  It is in nice condition.  It has a date on the back of 1962.

The red one vintage is also a slide socket screw calculator by (or so it says on the card "buy") Unbrako.  It measures about 8" x 3 1/4".  Seen in my photo you slide the inside card to the correct "A" diameter and it adjusts all the other dimensions on the card...ctr bore, body drill, threads per inch and tap drill size.  It was made by Standard Pressed Steel Co.  It is in nice condition.

2 Slide Socket pocket tools Vintage items

$18.95Price