Hydraulic Fittings - Female JIC vs. Female NPT

NPT fittings have a fairly pronounced taper that you can normally see. I have more difficulty with the British pipe threads and the AN fittings. Generally, most manufacturers will provide some identification (the AN vs JIC mixup is fairly common), sometimes grooves on the nut or a number stamped on. If you've got a mixture of suppliers, I don't know anyway other than to gauge them. If they're bigger than about 3/4", you should be able to see the taper seat.