| Since porcelain does not rust, chances are they are mineral deposits.
| Depending on the age and prior care of the bowl, it can be scratched
| so they get a good hold.
|

The bowl is not worn at all, but actually rust stains
are not unusual. I was on a job awhile back with a
sloppy plumber who'd cut out a cast iron stack pipe
and got dust on the tub. The owner was unable to
get the stain out. Rust can also show up around drain
flanges in sinks and tubs. (Stainless steel can sometimes
give off a bit of rust.)

But I don't actually know if rust is what I'm dealing
with. It looks like the tenant put something in the bowl
that they shouldn't have, before they left, and it sat
there for days. Now there are just these tiny rust-color
specks.

| My first choice for toilets is bleach, second is brush, third is a
| razor blade.

So far I've tried "CLR" and scrubbing. Before that
I tried ammonia. I read that bleach is bad if it's
rust and that leeching the rust into an acid is the
trick. But you might be right. It's possible that I'm
dealing with specks of something stuck to the bowl
and not a stain at all.