Flow Lines On Proof

It is possible and I've seen lots... Let's see if I can find one for you...

Reverse 2003 S Roosevelt Proof Dime graded PR69DCAM by PCGS:


(there are flow lines in the obverse, too - especially around the bust, but they're not as easily seen)

-edited because I put the wrong danged image up the first time!-

I guess flow lines on proof coins are more possible when the proof dies are near the end of their working life.
50 years ago and earlier, only a tiny number of coins were struck off proof dies, mostly for record and registration purposes. However, in this commercial World where a mint may produce millions of proof coins for a huge profit, there is strong emphasis the extend the working life of proof dies as far as is possible.

Good point, Conder101.

Another thing that I think is important to understand is that now, that "ultra cameo" is built-in to the design of the die in such a pronounced matter that a truly modern proof - in the last ten years or so - will almost ALWAYS have that ultra cameo look. Dies were different before then. It's shocking to look at modern proof cameo and ultra cameo coins compared to more vintage ones.

So things like flow lines are definitely something to look for if you're working on a high quality proof set, beyond the grade and the holder (something you should obviously do anyway).