Shimano Altus AX (AT30 2nd style) derailleur

The Shimano Altus AX (AT30) is the most idiosyncratic of Shimano's famous AX family of 'aero' derailleurs. Unlike all the other models, it was never indexed. Unlike all the other models, it does not have a distinctive cuved cable guide, its adjustment screws are perfectly normal and placed conventionally, and, strangest of all, it continues the Altus family tradition of having the cable clamp bolt mounted on a sprung 'Centeron' lever. Even its styling is a touch racier - with tapering parallelogram plates.

Finally, it is not shown in the January 1981 'Shimano aero dynamics' catalogue that launched the range, and it does not even appear in the all-encompassing April 1982 edition of 'Shimano Bicycle System Components'.

Despite this invisibility, it was probably the most tolerant, most reliable and least generally problematic of all the AX derailleurs. Dull-but-virtuous meets aero-science-fiction-chic.

It wouldn't be an AX series derailleur if it had not enjoyed multiple minor revisions over its very brief life. The various versions include:

The very first versions (mid 1981?) had a screwdriver headed p-pivot bolt - in the Shimano style that can accept a flat blade and a Philips head screwdriver. It also had an inner pulley cage plate that was quite pointed at the tension pulley, and a relatively thin, light grey, plastic spoke protector - also at the tension pulley.
The second generation (late 1981?) had an Allen key p-pivot bolt and a redesigned inner pulley cage plate that was more angular at the tension pulley. It continued with the thin, light grey spoke protector.
The third iteration was idenitcal to the second, except that it had a dark grey spoke protector that was more extravagantly shaped and relatively thick.

This is a very presentable, unused, example of a second generation Shimano Altus AX (AT30). It has an Allen key p-pivot bolt and a light grey, relatively thin, plastic spoke protector disc on the inside of the tension pulley.