c534 receivers don't have serial numbers and only can pair two devices
c534 are limited receivers. They don't have serial numbers and can only pair a limited number of devices.
There is special code to handle them that gives them a serial number of 0 (the integer) and pairing number of 6. Both cause problems.
idefix testing> ../bin/solaar -D /dev/hidraw10 show 99 solaar: error: 'int' object has no attribute 'lower'
This happens because 0 is not a string.
Setting the pairing number to 6 give a very false impression of the receiver.
A fix is in the works.