Just downloaded and installed the Mac wallet. It still shows V1.5.1. Is that correct?

Hmm, I have not seen that one and do own a MAC, so not sure, I will have to check. But pretty sure, it should say 1.5.2 like the others. Did you download it from the Github site or from where?
Downloaded from the Guncoin website..
I just downloaded from Github, and it says 1.5.3 now. So, you should check your linked download on your website...
V1.5.3 is the correct code as of today that you should be running.