Man -- that brings back memories. Just for "kicks and giggles" I took a quick inventory of all the portable tach/dwell units I still have. Surprisingly there are a few.
I still have the first Dwell/Tach I ever bought back in the day. At that time there was a company Rite Autotronics Corp. (aka RAC) that dominated the DIY market with bargain test equipment and battery chargers -- all US made stuff, but definitely for the low end of the market. I still have the old vacuum gauge, compression tester, dwell/tach, and several nice battey chargers from RAC. The cheap RAC non-powered timing light went in the trash decades ago though.
This image is from the net, buy mine is in the same shape -- sitting in a box in the attic somewhere. First dwell/tach I ever owned that was exclusively mine. I usually had to borrow dad's or grandpa's when working on cars myself.
These others are sitting in the garage today --
Old Hawk -- tach/dwell/multimeter
Sun Automotive professional tach/dwell meter
Sears Automotive Engine Analyzer tach/dwell unit (perfect shape)
Stewart Warner handheld tach/dwell unit
Some of you older guys probably also have some of these things stashed away in boxes. The problem these days is trying to explain what these things were used for. Most kids have never seen a distributor -- or if they have, they've probably only seen electronic distributors. They don't understand the technology associated with older point type systems.