I found an 870 Express Magnum for $285 which the dealer says is the one that Law Enforcement purchases because they no longer put the word "Police" on the side.
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Mr. E,
I don't think so.
Take a look at
http://www.remingtonle.com/shotguns/870.htm . Note the model numbers/order numbers on the variety of 870Ps listed on the various pages linked from there. Ask your Remington Factory Certified Expert Dealer Information Dispenser (TM) what specific model number is on the box for the Express gun he's trying to pass off on you as an 870P. See if it matches any of the model numbers on the list of 870Ps you jotted down. I think you'll discover that it's a different model number and that any recently manufactured 870P is going to have POLICE MAGNUM stamped into the side of the receiver as big as life.
I have seen a lot of dealers lately offering the 870 18" barrel, synthetic furniture Express models (with and without the 2-shot magazine extension) to the unsuspecting public as Police or Law Enforcement guns. Ain't so, sorry. They used to list them as Home Defense (HD) models, now they are just one more variety of Express guns.
It's up to you to be an edumacated consumer or you will forever be getting ripped off. An Express gun ain't a Police gun and the prices are likely to be about $100 apart. Back in the old days when I was buying my first used 870s (the early 1970s) all 870s were marked Wingmaster and that was it. The Police guns had 18" cylinder choke barrels, the Riot guns had 20" cylinder choke barrels and that was how you told the difference.
Nowadays things are more complicated. If you just gotta gotta gotta have a Police gun, order one from one of the distributors that sells them and get a gin-you-wine brand new in the box POlice gun sent to your local FFL dealer. Or buy a used law enforcement trade-in, if you can find one. They do turn up from time to time.
But if I were you and I just wanted a good 870, I wouldn't bother. I'd just go find a good solid used 870, be it Wingmaster, Police or (older) Express gun, and be happy. I have all three versions, more than one of each, and I can't tell that it makes any real difference which one you buy. The most I ever paid for any used 870 was $270 for the trade-in 870P (marked POLICE MAGNUM), it was almost new condition with nice walnut furniture and a polished blue finish, it was made in 1989 according to the serial number (Remington will tell you your gun's year of manufacture if you call them at their toll free number and give them the serial number). That was about $100 less than a brand new 870P of the same model would cost at the time.
Yes, some of the springs are a bit beefier on an 870P. No big deal, certainly not enough of a big deal to pay an extra hundred bucks for IMO. Chances are you are not going to wear out any 870 no matter what model, no matter what springs are in it. Magazine springs need replacing every so often anyway, just replace it with a heavier Wilson or whatever spring when you do. The shell stops aren't likely to wear out, neither is the trigger return spring, and AFAIK those are the only springs that are heavier in the 870P.
Even an older model Express gun is still a heck of a tough pumpgun, I'd rather have an older one in good shape (no magazine tube dimples, aluminum trigger plate instead of plastic) than a brand new one. They turn up on the used racks pretty often, in good enough shape to consider bringing home and at bargain prices to boot.
If you really want a real 870P no matter what the price, find one that says 870 POLICE on the side. Drop a note to Kevin Wells at Discreet Ordnance (kevinDOTwells(AT)disc-ordDOTcom, substiture . for DOT and @ for (AT) of course), see what he can do for you on prices for a new 870P shipped to the local FFL of your choice.
lpl/nc (unless things have changed lately with how Remington marks 870s, I'd be looking for a different dealer. Ask Kevin when you email him, he sees brand new 870Ps often and I don't)