Review this page: Member Policies: AMF, CPE, Retired Status & Vouchers (isc2.org)
Section 4.4 is what you'll deal with. Because I didn't know any (ISC)2 members who could reasonably endorse me, here's what I had to do:
I composed a description of responsibilities which I held with my employer at the time, and asked HR to compose a signed letter which stated:
- my current tenure with the company
- a list of security roles which I had performed
- exactly how long I had held the responsibility of those security roles
This letter was submitted to (ISC)2 as instructed, and my endorsement didn't take much longer to complete.
Also, congratulations! Well done.
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A claim is as good as its veracity.