Parker 51 question

I have found a Parker 51 vacumatic in the wild. The store is asking $35 but will take $28. Would that be a faire price if it is in good shape. Also, any tips on what to look for? I'm planning on taking some ink to try to dip test the nib in the store. I gave it a quick look over lunch yesterday and it looks in good shape, maybe just a little clean-up.

Thanks

Good price if it is in good condition, except for the diaphragm. Expect that it needs to be replaced, and don't try to fill the pen with ink. Use water instead, only use ink for dip testing.

I'd consider it to be a fair price assuming that the nib is in good shape and there aren't any visible cracks. As Johant suggested, with any Parker vac, I assume that the diaphragm will need replacing as it does most of the time. If you're going to send it out for repair, you'd need to factor in the repair cost (~$25-30) to determine if the overall cost is worth it to you. The repair work isn't necessarily that hard, but it does require at least one unique tool.