have had a quick look at the EW films + checked a couple - the dates on the boxes correspond to the LDS dates and in the couple I checked these dates matched what was on the film - the index (name + frame number on film )appears to be correct but the reported years covered (in the printed index pages) seem to be incorrect - it would appear that one LDS film which possibly duplicates wills held on adjacent films is not included in the Manx Museum EW series.
I have also looked at EW21 which covered 1676-1678 - BL gives an index to LDS 0991643 which also according to him includes 1675 - the actual EW21 film has one book of 1676 wills, then a book 1677-2 (cover marked second circut) then 1677 (a torn and mostly missing cover but marked 1677 and which I assumed to be 1st circuit) then two circuits for 1678

I havn't managed to reconcile the some 100 names that BL has for 1675 on 0991643 with the entries on ew20 or ew21 - something is very strange here