Check the forend,,they split very easily and most seem to be. The split usually runs from the receiver forward.
Aftermarket replacement wood is available.
Check for matching ser# on the upper and lower.
Magazines aren't ser#'d IIRC, but make sure the mag is a Winchester original, not an aftermarket if paying top price.
Originals can cost you $75 and up (usually up) for the 5shot,,the 10shot mag is more.
The 5 shot 351/401 original magazines are a one piece drawn steel construction. Not a stamped steel welded together design. I'm not sure of the 10shot 351 mag, but I think it is the same construction.
Field strip/TD is usually as far as most people should go when taking any of these apart. If you want to go farther you'll need a spanner type wrench to loosen the bbl nut. You can make one simple enough, some of the shotgun choke spanner wrench tools fit nicely. Beretta & Winchester but I don't know the particular model of choke tube they're for.
Be very carefull taking the recoil spring out. It's under a lot of tension. If you've taken a Winchester 63 apart, it's much the same, but on spring steroids.
The Police Model will have a fixed rear sight in the dovetail which is a little closer to the breech end than the sporter bbl.
The barrel will have a larger muzzle diameter than the sporters. The larger diameter is for the bayonet mount to slide onto & lock. The mount then has it's own front sight on it. Heavier stock and forend. Cocking hook on the op-rod I think and military style sling swivels.
They are usually priced considerable higher than the sporters.
Don't confuse an 07 used by a Police Dept with a 07 Police Model.
Though the former if it can be proved will generally increase the value as well over a plain sporting model in the same condition.
No .351SL in the group now. I do have a Model 1910 401SL and it gets out to the range when I can find ammo making time.