For $30 you can risk getting robbed , it's only about the price four films :)
I have a Petri E.Bn rangefinder with the 4.5cm f/1.9 Orikkor lens and it's a very nice user camera. All mechanical, no batteries but has an old "bug-eye' selenium cell light meter which still works! Sort of. Fun to use and takes excellent pictures. My wife brought it home from an auction; she paid $4 or $7 for it, I can't recall.
You paid too much by most standards. I regularly buy these types of cameras for $5. However, the lens is very sharp. Check for internal haze by cleaning both the front and rear elements and then, with shutter on BULB, open the back and at widest aperture, fire the shutter and hold it open: through the back, look through the lens at a bright light and you will see if there is internal haze or excess dust. I take mine apart for cleaning of all the elements with Windex or even (gasp!!!) straight household ammonia (EXCELLENT CLEANER, HONEST). Plain water does not cut down on static like the Windex or ammonia does. REALLY CLEAN are my lenses, inside and out.
I would recommend the following: with wide open aperture to limit depth of field, shoot the 'picket fence' type object (ie, something diagonal so you can see if there is a difference between what the RF says is in focus and what the film plane actually records). This is VERY important to do because, oftentimes, the two are out of alignment.
If you decide that there is a difference here you will either have to remove the top to align properly or, as is the case with most people not knowing how to change the alignment, adjust for the proper focus by moving the focus ring to compensate. For example, if your RF says the 10 ft is in focus and the film plane actually delivers about 50 ft that is in focus and 10 ft is NOT in focus, then you know that whenever you focus at '10 ft' (according to your rangefinder) you will be ACTUALLY focusing at 50 ft. You would have to move the focus ring so the the lens moves OUTWARD slightly to bring the ACTUAL focus closer (to 10 FT0 than the ACTUAL 50 ft distance that was focused upon according to the film plane.
Perhaps a bit confusing to digest at first but re-read carefully: in summation, if you are ACTUALLY focusing at 50 ft (NOT NECESSARILY WHAT YOUR RF TELLS YOU!) you have to rack the lens out slightly in order to ACTUALLY focus at only 10 FT. The rangefinder is an INDICATION, not an ACTUALITY. Sorry for the prolixity but I do not know how to express more succinctly.
As a consolation: the lens is VERY sharp if, and only if, you are ACTUALLY focused at the correct distance. This misalignment is the cause of many stating that their lens is not so sharp when it really is. I have never in my life 'visited' a lens from Japan that was not tack sharp except for the wide open status of some 'miscellaneous brand SLR wide angles (but were sharp stopped down). Your rangefinder does not suffer from the 'computation compromise' that many older SLR wide angles suffered because, with rangefinders, you have no mirror to worry about getting in the way of the rear element. - David Lyga
David, found this thread and want to thank you for good advice. I may just buy one as I am having poor luck with Electro's. I am really starting to hate anything with electronics and I am a licensed Ham.