From Quora:
Early in my Masonic career I was asked this question by another Mason. I answered truthfully and then asked why he asked. His answer was that he had heard that I was a Mason but he wasn’t too sure and this was why he asked. We then exchanged some other Masonic Language and were mutually assured that we were both Masons.
This was only the first time I ran across this question and it was only a polite means of asking if I was actually a Mason. While traveling I also asked a man this same question when I was in a parking lot and he had just emerged from a car with a Masonic decal on the back. He gave me a prompt answer and we exchanged handshakes. I told him I was new to the location and was able to ask questions about where I was and felt assured I was getting a proper answer to my questions.
