The Tektronix P510A is a 10x passive voltage probe.
Maximum voltage is 600 V peak-to-peak. It connects to the scope with a UHF connector.
It was made for slower Tek scopes, up to Type 535. The cable is standard 50 Ω coax, which rings above 10 MHz. This aberration is not visible on slower displays, but the 30 MHz Type 545 necessitated a new probe, the P400 Series.