Need specifications to operate this stepper motor with RPi or Arduino
You should be able to Ohm-out the connections.  You have 5 points that will be connected to a set of coils somehow.  Figure each coil will have the same DC resistance, so by measuring the resistances between various combinations and comparing then, you can find out how many coils are in the path between any two leads.  From that you can probably determine how the coils are arranged.

Usually these motors have three coils connected in one place, so a total of 4 connections.  Maybe yours has 4 coils, or maybe just a chassis ground wire or something.  Given that 8 coils are visible in the picture, I'd guess you have 4 separate windings with one common.  Again, Ohming it out should answer these questions.

Once you find how to energize individual coils, try each separately and observe where the rotor goes.  The movements will be small, but you should be able to figure out the sequence.

Then you need to determine the maximum current it can handle.  The limiting factor is how hot it gets.  Try a few currents.  Run it at each current for a few minutes or until you think it gets too hot.  There is no size reference in your picture, but I'd probably start with 1 A and then go from there after seeing how warm it gets.  With everything closed up, a conservative temperature is if you can just about hold the motor in your hand for 10 seconds or so.  The inside will be hotter, but if the outside is just at the human discomfort level, then it should be fine.