Most police departments forbid the use of saps, slaps and beavertails.
Some smaller departments will turn a blind eye towards the carry of such, but you better check with a veteran.
My first Sheriff actively encouraged the use of a lead slapper. Used properly, I have found that the wide slapper/beavertail is -- at its worst -- every bit as good as an expandable baton.
At its best, a slapper is much more effective than the baton.
Palm saps are sneaky little jewels. Mine was a disc of lead encased in leather about an inch, maybe an inch-and-a-bit in diametre. It was attached to a leather loop in such a way that the lead was held in the palm, with the loop across the back of the hand.
An open-handed, jovial "hey-buddy-how-ya-doin'?" smack to the elbow, bicep, floating ribs or thigh caused a drunken redneck or three to reconsider their options.
An open slap to the head or jaw would probably knock someone cold, but I never had to go that far.
Sap gloves are bloody good in-fighting tools. They are both more versatile than a slapper, and at the same time, less versatile.
While wearing sap gloves it is possible to use your hands to do other things -- grabbing a subject, applying handcuffs, dailing phone, etc.- while still keeping the weapon on paw, so to speak.
However, having the lead shot spread across the back of you knuckles limits you to punches and backfist/backhand shots.
Effective, but Sheriffs and Chiefs of Police tend to start developing heartburn upon seeing a vidcam shot on the evening news of one of their officers back-handing a critter, even if the critter really, really needed it.
With a slapper, or palm sap, you can be a little more discrete and still get the job done without that nasty closed-fist punch, or back-of-the-hand pimp-slap that doesn't really look good on CNN.
LawDog
OUCH. It's not exactly "concealed carry" but no point in escalating if you don't have to. Nobody ever asked me why I have a pair of cattleman's gloves tucked into my pocket, and hey, whatever you have stuck in the finger(s) just drops right out if you actually need the gloves.... 
Thought I remembered these from drafting classes long ago!
