What models use "HP-48 style" enter?

[Carsen]

I don't have an answer to your question but I may have information that can help you answer it.

The "HP-48 style" enter is used on calculators that deal with...

• A Command Line (Entry Line in Prime's case)
• The stack deals with many, many different types of objects.
• Tend to have a large stack.
  

The "old" behavior, as you call it, is used on calculators that have...

• 4 or 3 level stacks.
• Input numbers directly on the stack through the X-register.
  

I believe these are the main differences that would influence the different ENTER key behaviors. I can't think of any more at the moment.

Keep in mind HP never abandoned either styles and both are used in today's HP calculators.