Rollinia mucosa/deliciosa seeds do not keep. Some of the other Rollinia species probably do keep, but I have not tested that.
Guanabanus, I believe you are right, probably under the name Rollinia mucosa
few Rollinia species seeds are distributed, wrongfully but maybe not deliberately
That topic made me bit curious, To set an experiment I've purchased today
seeds from honest seller in Europe, His seeds came from source I know
but won't mention neither of them not to damage anyone.
The seeds stock is few months old and described as Rollinia deliciosa
According to the seller no one complained about bad seeds
And for my knowledge he wont risk his reputation just to catch few gullible buyers
If and When the seeds arrive I'll weight and measure them before planting few.
My phone camera is old but I'll try to take few photos as well
And inform if something interesting happen
There is surely a certain degree of confusion
http://www.montosogardens.com/rollinia_mucosa.htmPropagation and Culture
Biriba is usually grown from seed, but superior cultivars may be propagated by grafting. It can be grafted onto rootstocks of Annona montana or Annona glabra, which causes dwarfing. Seeds remain viable for up to 3 years if they are kept cool and dry.