HP67 - How to display the mantissa

[Mike T.]

I have never owned a real HP67 only use my HP67 simulator occasionally so I may have missed something obvious but on (most of) the Spice and the Voyager you can display the mantissa using 'clear prefix', or 'mant' functions.

However, I can't see a way to achieve the same thing on the HP67. Was this feature only introduced later? The first machine I owned was an HP31E and I know that could do it.