Adler 81 C Calculator

Adler 81 C basic 4 function calculator with pouch (pouch has slight rip on side). From the 1970's. Takes 4 AAA cells and has a mains adapter socket but I have no idea if the adapter would charge the cells or would replace the cells. Vacuum fluorecent display. Cosmetically good but has some wear.
Tested and does sums and the switches do stuff.
The battery compartment is accessed by sliding the whole back cover.