NSpire NSP-201SE (Silver).  Most were black and sold under the Thermaltake brand name, but this is from the OEM (NSpire).  Photos are accurate.  Item is brand new -- I bought two, only used one and realized that I need fewer duplicate tools as I do more workbench work than I do work on the road.  Perfect condition.

Want to know how to use it?  Read this article:  
https://www.thetechmentor.com/posts/how-test-power-supply-using-nspire-power-tester-plus/

o  Test P/S 3.3V, 5V and 12V Voltage Output
o  Compatible with Molex connector, 4P, CPU P4, FDD, S-ATA, ATX 20/24 connector
o  +3.3V, +5V, +12V Voltage Output Testing
o  Green LED and Beep indidate test result
o  For ATX 12V Ver. 2.0/1.3(backward support ready)