First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve
Indicator. This unit was developed in the 1970's and has been offered in a
couple of different variations since then. There is considerable controversy
over just what the LRI actually measures and how it operates, but when the
price of the analog unit was recently reduced substantially, it got my
attention. Since the panel of 399SB is rather unconventional, I had included
a small backup airspeed indicator. However, the AI was never used since I
rely on the RMI uEncoder for pitot info, so I decided to replace the AI with
the LRI since it could also serve as a backup airspeed indicator. The
decision was easier since the LRI would fit in the same space as the little
AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack