I have two types of relays to add to the collection.
First up is a Stepper Relay with 10 positions.
Stepper Relay
2P10T
(KO) D55541-A-9
Stepper Relay 2P10T. Advance rotor each time coil pulsed. Release coil can be pulsed @ anytime to start rotation again. Advance coil 60 Ω 12-24v DC. Release coil 50 Ω 12v DC. 4 1/4″ x 3 3/4″ x 1 1/4″W.
Any time you have a multi segment display, or a need to have ‘logic’ in your circuit, this would work well. for it will remember how many pulses, and can be reset at any time.
A relay like this is what made the original phone exchanges possible, without the need for the operator to connect you. Imagine a set of 7 of these, and with each dial of the phone that relay would move that many steps. ( old rotary phones worked this way ) you would physically step your way through an exchange with your number sequence to connect your call to the right outgoing line! How cool!
Next up is a latching relay, I was not able to find much info on this one for it is much older. Pre war possibly.
This type of relay would be used in a place you need the circuit to have ‘memory’ If you lost power, or need a state to stay with no power, this was the relay that would do the trick. You energize one coil to ‘latch’ the relay closed, and it will stay forever, the next coil, will release this latch and let it open again. A ‘Start’/ ‘Stop’ style switch system for a motor could work well with a relay like this. No other logic is needed.
Let me know in the comments if you have any cool use case ideas for these I should try!