Yup that's exactly what it looks like. My original drums had those on my '99.

Maybe take off the wheel (if needed) and look for a fresh rusty spot in that shape on the outside of the drums.

'99 Tacoma Xtra cab V6 TRD
TRD Supercharged, URD 7th injector and 2.2" pulley, 32X11.5 BFG All-Terrains, OME 881 3-inch lift/Toytec AAL, 5100 Series Bilsteins all around, and ProComp 130 lights.
No I'm not some creepy naked guy...