1. Both types (SMA & RP-SMA) Males have JACKETS
2. Females have thread on the outside
3. Then it’s just working out if it’s RP or not!
If the pin (known as Male), matches a Male jacket it’s just a plain old SMA-Male, else its “RP-SMA-Male” (no pin with jacket). Go with it!
If a Female (thread on outside) matches a lack of pin in the centre, and it’s a match (Female- Female) it would be a plain old SMA.
If it was RP then it’s the opposite. (Jacket and Pin).
If it’s an opposite (Female – Male) then it’s a RP-SMA (Reverse Polarity) connector!