Ian Gambini found the first 3 SPSSs of this order in the 1990s. Jim Williams found 5099308 in 2013. Brian Trial found 1425 in 2014.
It is estimated there are approximately 1.5 x 10^10 SPSSs in order 44.
A listing of the known tablecodes is available as spsso44.txt.zip. The file size is 464 Mb