Electrically, this is simple, shouldn't be a problem for anyone here. Mechanically is where issues are likely to arise. How far apart are the ring? If it's far enough, then your pins could be replaced by precision switches that then connect to the LEDs/buzzer, etc, but the ones I'm thinking need at least a 5mm threaded hole for mounting. Is that too big?However, it begs the question about the application: this looks to be a case where it would be simple enough to visually confirm that all the rings are in place. It doesn't seem like your customer is looking for any kind of an automated system (i.e., record on a PC that item #xxyyzz passed). Are the rings low-profile enough that visual confirmation would be difficult without the tool you designed, or is there something obvious I'm missing?