Hand Held Products 71M/M eprom carrier question

[rprosperi]

There are 2 different HHP 71 EPROM Carrier types.

The most common type has 3 pins in the upper-right area of the board (assuming pin1 in upper left orientation) used for selecting between 32KB (leftmost pair) and 16KB (rightmost pair).

The other (later?) type has 2 pins in the upper left AND 2 pins in the upper right of the board (same orientation). I've never found specific documentation for this second style, the manuals I have only explain the initial style, though I've assumed that it is used mechanically the same way - left pair for 32KB vs. right pair for 16KB.

I wonder if the 'other', less common type was introduced later to allow use of CMOS EPROM chips? This type has 2 transistors where the other style has only 1. I don't know enough about h/w to have any idea if this could make sense.

Here's a link with 2 photos, showing both carriers side-by-side, in the hopes someone might be able to tell:

https://1drv.ms/u/s!AiI5Ei2M2Ja2mH0S6o1n...k?e=m5QPe3