Double flowers will make this cultivar you have valuable as an ornamental. (That's certainly the case with flowering cherries and crabapple) A nursery that specializes in cold hardy citrus may be interested in it. (You might offer to send them a cutting later when your tree is much bigger)
I would guess whatever you have was probably grown from seed, since US 852 is used as a rootstock. The vast majority of the time the seeds are genetically identical to the fruit parent, but it looks like you may have gotten one of the rare ones that wasn't.
I think what you have may be very rare.