Which HP calculator had "The New Accuracy" first?

[J-F Garnier]

In the article of the HP Journal introducing the HP21/22/25 (reproduced here) we can read this:

"To improve the final results given by the HP-22, improvements were made to the standard HP-21- family arithmetic subroutines. The y^x algorithm was extended to handle negative numbers to integer powers--for example (-2)^2 or (-2)^-2--and a subroutine was developed to calculate the expression (1 +y)^x, which occurs frequently in financial equations. "

J-F