Hi Christina,
I'm sorry to say there is no way of knowing what hackney was the sire of Music Man. That's why on these pedigrees when you click on a line and it doesn't go anywhere it means it stops there. It just show's up as "unknown".
Under our present rules for the Foundation seal...there has to be four generations of no "B" papered pony in the background. "B" being modern blood (which includes the Hackney or Welsh blood) that were bred into these ponies years ago.
Right now I have a Classic Mare that also have some "B" blood in her fourth generation, but all of her offsprings (if fillys) when bred and foal, their babies can carry the Foundation Seal for the fourth generation will stop at the current baby. For the showring, the only qualification for showing a Foundation Sealed pony is that they must be 42" and Under.
Lyn and some of the others on this list has some really nice ponies that are from the Taylor Pony Farm, that are also double registered, some due to height being small enough to register as a mini, but for the most part are still Shetlands(ASPC/AMHR) and some of those double registered ponies carry the Foundation Seal because they don't have any "B" papered pony in their background for four generations.
I have one Classic Gelding that in his fourth generation does have a Hackney in his background. But due to the number of "B" or certain percentages (12.5% or 1/8 or less) they can carry "A" papers.
As posted earlier, the only other person that would possibly know anything more on the Americana line would be Scott Uzzel as he has a lot of history regarding the Shetlands from back in the 50's.
If you bought that pony from Jackie Tyler you might want to contact her to see by chance she may know. If she bought it from someone else though, she may not know either.
Thanks.
Karen Shaw