You missed that these are 149 sized with comparable nibs. BB on the 90, OBB on the Blue Hour.
Sorry, I did miss something.
I was talking my 90th anniversary 146 the other day - I didn't realise pwsuba was talking about your earlier post, also about 90th anniversary pens. Mine is a fairly plain rose-gold 146 with 90th Anniversary engraved/stamped on the nib.