When you had the last LPC/prof. check/LST or revalidation by experience, the FE should have completed both page 1 and 2 of SRG\1119. Page 2 has a "level 6" declaration. If this wasn't done, and make sure you have the correct issue of this form (issue 15), then you can have a stand alone declaration c/o SRG\1199.
ps, If you read the notes carefully for SRG\1119, you find that this evaluation can be made, even if the form is used for "revalidation by experience", and not a test. An FE should be able to sign this, as they also should have covered this in their 3 yearly revalidation.