Going through the album I bought a couple of weeks ago, I found these. 1945-P appears to be RPM-002 on variety vista, P/P/P/P. I can easily see three of the P’s but I’m not sure where the fourth is. Next is a 1945-S with something odd on the rim. All I can think that it might be is a cracked planchette; if not damage. I hope the photos are clear enough to see what’s going on. Best I can do with my 5 year old iPhone.
The photo of Wexler's WRPM-001 looks closer to your coin than the one shown on VarietyVista. IMO http://doubleddie.com/1469045.html Here you can see the line under the P The 45 S looks like damage. EDIT. Looking closer, it could be a cracked planchet.
The arrows on Wexler's site show where the 3 secondary Ps are. Two have large spreads, one north, one south, and the third is pretty tight against the bottom outside edge of the loop of the P. Lots of cool RPMs on war nickels. The mint mark punch being so large made it more difficult to punch completely. The 45-S is a defective planchet. It might even be a bit thin near the cracked part.
I think your coin is an earlier die state of the RPM-002 than Variety Vista has listed. You should contact James Wiles at CONECA and have him take photos of your coin, to add to his database. While this is a fairly prominent RPM, there are 91 RPMs listed for 45P. These are quite common. This is one of the best ones, but it won't sell for a huge premium.