Wire gauge, but for what sizes?

I picked up this, what I thought to be a drill size gauge, at a car boot sale recently -



Though, having a google about, it appears to be a wire size gauge as the cut-outs are similar in shape to this one on fleabay -



But I cannot work out what wire size series it is for. The holes do not correspond to SWG.

Any ideas anyone?

The slots are the measure, not the hole, I reckon.
Could be imperial Sheet Metal gauge, perhaps. 22 gauge is 25 thou, if you still have feelers in "real" sizes rather than metric! 18 gauge is 40 thou.
(Imperial Wire gauge... 22 gauge is about 28 thou, 19 gauge is 40 thou ...1 mm near as-)

hotbulb said:

The slots are the measure, not the hole, I reckon.

Click to expand...

Ah okay, that does make more sense.

hotbulb said:

Could be imperial Sheet Metal gauge, perhaps. 22 gauge is 25 thou, if you still have feelers in "real" sizes rather than metric! 18 gauge is 40 thou.
(Imperial Wire gauge... 22 gauge is about 28 thou, 19 gauge is 40 thou ...1 mm near as-)

Click to expand...

I shall get my vernier calipers and feeler gauges out (both metric and imperial) and have a see.

Thanks.

Yep, measuring the gaps rather than the holes shows this to be a Standard Wire Gauge.

This popped up this morning!
Wire Thickness Measuring 2 Sides Round Wire Thickness Measurer Tester Ruler Gauge Diameter Tool
I suspect it's American Wire Gauge.

Should have been clearer. It's a standard wire gauge for Standard Wire Gauge. British Standard Wire Gauge to give its full title - as defined in BS 3737:1964. Wikipedia has all the details - standard wire gauge