For SMA and RP-SMA, SMA connector was the original specification used to the market.

Due to its operating frequency characteristics, small size, and light weight, it is highly suitable for wireless development in the microwave field.
 

To segment the different applications and prevent incorrect connections in mass usage, the RP-SMA (Reverse Polarity SMA) connector was developed.
 

With the advantages and practicality, SMA type connectors have been designed in wider and deeper adoption worldwide.

Therefore, how to make a clear distinction of SMA and RP-SMA, let's see  https://www.lihyeu.com.tw/support.php?cid=2