Let me take a whack at this: First, series 7 licenses cannot be grandfathered. More importantly, if your licenses has expired, you can affiliate with both a FINRA regulated firm, or a PHLX regulated firm provided you can show you have been actively engaged in the investment business during the interim period. You will however need a letter from the prop firms on THEIR letterhead verifying your employment and duties. The PHLX uses the Central Records Depository (CRD) system operated by FINRA, the ole NASDR. Most firms are loathe to put anything down on their letterhead, and depending on how you left that may be a hurdle to overcome. You can contact the FINRA Ombudsman who may be able to assist since your 7 recently expired. You can find the contact info w/ a simple search.
I'll try to contact FINRA. Im a bit confused about all these regulatory body's. Whats the difference between FINRA, NASD and who ever else? Pardon my ignorance. I've never had to worry about these things as a prop trader. Also, how about my 24 and 55? What might there status be? Thanks for clarifying things.