Is it safe to assume that since it grew from seed last year, that it will do so again, and grow similar tomatoes given similar conditions? I guess I’m really asking if these seeds can be assumed to be non-hybrid, open pollinated. I already know that it is indeterminate, due to size and length of production. <<<
I can only give a granny answer and others may have one based on science.
First, try a few of the seeds and see what happens, start them indoors so you will have a head start and can maybe make a second planting, if it starts producing early.
My granny thought, is that it could be a hybrid of its own making and the saved seeds may not be good, but then it could be an old variety and it will be good.
You will not know, until you try them out.
Just be sure to plant other varieties, so you will have a crop.
* Is for heirloom seeds
On second thought, that may be the first two plantings. I don't think I have enough pots to do them all.