By probe, I assume you mean like this?
For me, a 100% must have.. It's my usual plucker of coins.
I rarely use a digger as for me, they tear up the grass worse
than a probe. I can pluck a coin with a probe, and two days
later you can hardly tell it. Most of the sod stays in place,
and I just cause a mini earthquake, and pull it up with a tear
in the sod. Once done, I can pack it back down, and you
can hardly see it. Every time I use a digger, I end up with
more damage that lasts longer.
Myself, I wouldn't pay too much for one. I make my own
from long screwdrivers. The blue handle version is from a
home depot 8 inch screwdriver that I blunted down with a
grinder and then polished. Works great, and is my usual
tool. The other is a pushrod from a ford engine, and was
my first probe. I used it because it had the pre made blunt
end. It worked fine, but I wanted a handle..
You want it pretty blunt and smooth to avoid scratching up
coins. Mine rarely damages one unless I really jam into it.
Anyway, I probably wouldn't pay more than $10 for a probe,
being I can make one so cheap...