Since I work a plainclothes assignment I've made it a practice to simply display both my flat badge & issued ID card, which contains my picture, as well as other information.
Naturally, I started doing this after some folks questioned my badge, displayed in a leather belt-clip type holder, and I had to start digging my ID card out of my wallet.
Then, I got an approved ID badge wallet, which contains a flat badge (duplicate of my regular badge, except its flat and glued in the wallet), and displays my ID card in a window opposite the badge.
Then, folks started questioning whether both were fake.
Sometimes I even display a second ID card, as well as a security-coded building entry card, which contains another picture of me, and is displayed in a pocket-clip holder, used for building security identification purposes.
Back when I was in a uniform and working an area which was a bit above 'middle class', I even had some folks tell me that my badge, ID card, uniform and marked patrol car could ALL be fake, and wanted to know how I planned on 'proving' my identity to their satisfaction.
No problem, just call the communications center and ask them to verify whether I work for the agency, and ask them to confirm whether it's me at your door. You want me to GIVE you the number??? Hmmm, no, I don't think so ... I think that to make this double-blind identity check effective, you should go look it up for yourself, while I wait outside, and try to figure out how to get transfered around the switchboard and communications center, and then to the specific dispatcher that handles such requests, for yourself. I'll wait outside and listen to the stereo ...
Of course, some folks who won't demonstrate at least some minimal common sense, in situations involving suspected criminal activity, sometimes end up being cuffed with fake cuffs, booked into the fake jail, and find themselves arguing with the fake judge ...
Now, our ID cards have changed over the years, and the new ones have a bar code, aren't laminated, and they're apparently 'more difficult' to produce, equipment-wise, than the older laminated ones.
ID cards can change from one agency to the next. Some have ID numbers on them, and some don't. Mine doesn't.
For that matter, some badge numbers are ID numbers, and some ID numbers don't match badge numbers. Some badges have names instead of numbers.
Some ID cards have holograms ... and some have smart chips.
Everyone is apparently consistent as hell, huh?