The Countess is a small rotary adding machine. It has a 7-digit register, which in this case is adapted for adding British currency. The last number wheel counts from 0 to 11 and represents pence. The next two columns represent shillings, so count from 00 to 19. The other four number wheels are normal decimal wheels to represent the number of pounds.
There are 7 vertical slots on the front containing large toothed wheels. These wheels can be turned by using your fingers. You can insert your finger next to the digit you want to enter, and pull it all the way down to the bottom of the slot. This action immediately adds that amount to the main register at the top. The small crank on the right hand side clears the register.
