This is the TI Concept II calculator. It was sold by a discount department store called Zayre's in the mid 70's and is basically a re-badged TI-1250.  In fact, it's exactly the same except for the colors on the faceplate.  It was introduced by Zayre in 1976 and retailed for about $17.00. It has a 8 digit red LED stick display, one memory register and ran on a 9 volt battery. It uses algebraic logic with 6 functions and 24 keys.

The Concept series from Zayre included the Concept 10, Concept 24, Concept I, Concept II, and Concept III.  The Concept 24 was made by Lloyd's while the latter three were made by Texas Instruments. The TI Concept II is not a real popular calculator with collectors but does have some novelty and was made by TI so it does have its place in a collection. The Concept II calculator will sell for $25-$70 depending upon condition and accessories. The Concept III is probably more rare and will sell for over $100.00.