Ian Gambini found the first 2 SPSSs of this order in the 1990s. Jim Williams found 4241397 in 2013. Brian Trial found 1155 in 2014.
It is estimated there are approximately 5.7 x 10^9 SPSSs in order 43.
A listing of the known tablecodes is available as spsso43.txt.zip. The file size is 372Mb