I believe that 19.43.1a is the latest firmware for the 29N3 hardware, which is the latest released (2020) hardware version we are aware of. Earlier version of the hardware (2019 & 2018) got a different version of the firmware with what appears to be a later version number, however we have no idea if 19.43.13 is newer (with additional updates, features, etc.) than 19.43.1a, has less or is somewhere in between. Hardware and firmware version numbers (and capabilities) have to match up to each other, so a 29N3 hardware will never get a 19.43.13 firmware, at least that is how I believe it works. It is also possible that the .1a is actually a later number than .13, we have no way of knowing their numbering system. It could go .11, .12, .13, ..., .1a, .1b, ... etc.