Those are 'vintage' devices only suited for pre ODBII-enabled vehicles. For garages that used to service 'lots' of vehicles they were quite essential but, over time, the DIY market filled with individual handheld products that achieved the same functionality - dwell angle measurement, timing lights and such stuff.
As a result, when ODBII et al came along (now a mandatory fit for all vehicles) such testers as the SUN EET1120/920 were obsolete and
can't even be used on modern vehicles at all.
If you can find a film crew that requires the use of one for 'cosmetic' purposes then it's value might amount to something but in the general meaning of the world at large it's as good as scrap.
Anyone that works on vintage vehicle engines will already possess the required test equipment.
Check out this link:
https://www.jalopyjournal.com/forum/threads/vintage-sun-1120-electronic-engine-tester.1040210/
and look at all the 'bumps' the guy tried to get someone interested. Yeah, he sold it - eventually - and actually got $350 for it (or so he says) but it sold, I presume, as a curiosity rather than a device for practical usage. Just goes to show, if you're prepared to WAIT and to advertise in the right places you MIGHT get something similar.