ENTER↑ is a misnomer, long live ENTER:

[hansklav]

(07-06-2014 04:38 PM)Katie Wasserman Wrote:  (…)
I think you have a typo in your post:

Quote: first RPL calculator (the HP-18C)

This should be: HP-28C.

It was not a typo. My source is the MoHPC.
According to the MoHPC the HP-18C was launched in 1986, and the HP-28C in 1987.

But I read that the HP-18C only used 'System RPL', and I don't know anything about the difference in the behaviour of the ENTER key between 'System RPL' and 'User RPL', so you might be right that the HP-28C was the first with 'Entry RPN'.

Hans