After you turn it on. If it works grab it.
Deal with any possible leaks once you own it.
If it does not work and locate targets air testing, offer $125.00, send it to me I'll give you $175.00
The 1280 is one of the best freshwater detectors out there, had one myself.
According to Fisher, main leakage problem the 1280 had was the battery compartment, the electronics are sealed in their own compartment.
About 8 years ago, Fisher charged me $40.00 to fix mine, add a new electronics seal and recalibrate it. I don't know about the current Fisher company....
I would grab it for $225.00 anyways, always make a profit on it if it went ebayishway.