Not at home to take a look, but it appears to me from the picture that the new HD 12mm has a longer black top to it then the original 12mm HD. Is this HD a little taller then the original??? (Like I said, not at home to check, so I could be wrong, it does appear longer in the picture.)
There seem to be two body format options to these eyepieces - the long format which match the Baader GO's and the shorter format which the Fujiyama's, sold by Lyra Optics in the UK, use.
The Astro Hutech's are the longer format except for the 6mm and 18mm which are "shorties".
The significance is the positioning of the field stop / focal plane which seems to be around 8mm further out with the shorter body format types.
The above is based on testing I've been doing with Baader GO's and a set of the Astro Hutech orthos.
Mixing the body formats as Astro Hutech have done messes up the par focality of their ortho range, which is slightly annoying.