The HP-41 was made in two different version.
Fullnut and Fullnut
The first versio was Fullnut.
It does have a CPU board innside the the unit.
The big problem with this was the plastic holding the screw for the cover.
They break quit easely and the CPU board does loos its conntection with the keyboard.
Here is a picture showing a workaround using two nuts to make it stick.
This 41C does also have to memory modules added internaly.
The new version, Halfnut does has a new design, no CPU board. The only board is the CX time module.
How to see the difference on the two version on the outside?
Look at the display.
The Fullnut does have square corner on the display.
The Halfnut has rounded corner.