The M55E was a light-tracking elliptical. It was rated at 0.75-2g by Shure, with a 0.2 mil contact radius. Its body was the same as that of the M44 series except for the model number printed on it.
You have all forgotten, or never knew about, the Shure M44E. It was a 0.4 mil x 0.7 mil elliptical, tracking at 1.75-4g. Its N44E stylus would fit and function in any M44 body.
Instead of speculation, most of the information on the M44/55 line is available for us to refer to, at:
http://www.shure.com/idc/groups/tech_pubs/@global_managed/documents/webcontent/us_pro_m55e_ug.pdf
...but even SHURE's listing on that page is missing one of the M44 series. That was the M44-5, which had the high compliance, light-tracking cantilever suspension of the M55E, but with a 0.5 mil spherical stylus.
Most of this is academic now. Some vendors such as turntableneedles.com still have old stock on the N55E and other genuine Shure styli, but for the most part all that is left other than genuine Shure N44-7 and N44G is a slew of aftermarket imitations from a myriad of anonymous makers. Many of them, even if claiming to replace the stylus on a cartridge that came from the factory with an elliptical or other advanced type, are actually sphericals, and some of those aren't even well polished. Even if an aftermarket imitation has a brand name on it or is sold by a specific retailer, that's no guarantee of quality. Many of them change sources according to who charges them the least. If a replacement stylus sounds different from the original manufacturer one, be suspicious and wonder why. If, as in the case of the Jico replacement for the Stanton 881S, the replacement sounds "a little brighter than original" (quote from a purchaser's review published on the Jico website), it is not a true replacement and the resultant Stanton cartridge with the Jico stylus does not sound like a Stanton. It sounds like a Jico.