Collection Item 

Casio Root 121A
Brand:  Casio. 
Model:  Root 121A. 
Origin:  Japan. 
Introduction:  1971. 
Type:  Basic compact but heavy desktop calculator with Nixie tubes display. 
Functions:  4Basic function, Square root, grand total (memory with limited functionality, see below), no constant. 
Display:  12 Nixie tubes. 
Keyboard:  19 reedswitch keys, On/Off switch. 
Main chips:  Nec D174B, uPD357D, uPD173D and other chips from Nec and Toshiba. I don't see any date code! 
Logic comments:  Pseudo RPN notation, very used at the beginning of the 70s, for example: To compute 2+5 you must type 2 =+ 5 =+. To compute 53 you must type 5 =+ 3 =. This calculator does not has the 0 error like many others of that time, but has the pseudo fixed decimal bug. For example if you type 1.25 =+ 3.75 =+ you will read 5.00, with 2 inneccesary zeroes. Square roots are always presented with a heading 0, for example Square(2) gives 01,4142135... Grand total always accumulates multiply and divide results, you will see this grand total pressing T and clear it with AC. 
Remarks:  Robust but compact casing with topquality plastics and other materials, operates with AC power, no batteries support. 
Size:  8.07 x 7.09 x 2.56 in, 205 x 180 x 65 mm. 
Condition:  (9.5/10) Excellent, no marks on casing, full working. 