Hi d'Angelo
I have been shopping and aquiring a few Acer palmatum cultivars lately, but the longest I have owned a maple has been about 4 years, so I am not an expert. From reading the catalogs, to really make an educated guess at which cultivar your maple grove is, you really need to take photos of the leaves and twigs in spring, summer, fall and twigs in winter. Once you have a set from all 4 seasons, you can sit down with various catalogs and go through. The selected cultivars have different colors for each season. Many may have leaves like yours in spring, but then some in summer green out completely, some don't, some in fall will turn bright red, some will be a blend of sunset colors, some will be the purest of yellows. There are thousands of named maple cultivars, and sorting through them is no small task. Vertrees wrote a complete listing of all JM cultivars known at the time he wrote, it has been revised once or twice, this would be the book to borrow to do some research for sorting out which cultivar it could be. (not sure you want to go through the expense of owning this tome, it is geared toward landscape use of maples)
So the easiest thing to do is just assume your grove is just the normal JM from seed and enjoy working with the really nice grove you got. Also, pay attention to the other trees, if there is slight differences in color through the seasons between the trees of the grove, then they all are most likely to be from a batch of seeds, each being genetically different. If they are all the same, then they came from rooted cuttings off the same tree. Regardless, at least for spring foliage they seem well matched to each other, like they might be cuttings off the same tree. That's good.