1988 $100.00 bank note

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Hi.  Can anybody tell me what the letters mean in the Charlton Paper money book, 2008 edition, page 332?   

BPN = back position
(CL) = clear position number
(H) = Hidden position number.

On my $100.00 note,1988 issue, I have found the plate number 66 I believe, but I do not know where to look for the other two mention. It makes a big difference in price at UNC. My note is AJX 3199953.
Any help is appreciated.
tommyboy

The explanation is on page 311, your note is BC-60aA-i.

Many thanks I did not see that page.
tommyboy