Seems plausible but unlikely.  Where are they?  Seems not too long ago a book on
metal planes of PA was published citing the range of sizes of jointers.  Almost
immediately somebody popped up with a bigger plane than listed.  A Hahn IIRC.
Publication of a new compendium is alway a point for someone to offer evidence
of errors or omissions, and a lot has been published about Stanley yet no
Stanley superjointers have cropped up.  Also, why give numbers to custom planes,
unless they are more made-on-request than custom.  Possibly patterns cast only
when requested?  But still where are they? Could they have all been scrapped?

Kevin