Nearly every comment made in this thread is accurate. When we distilled bourbon a decade ago, the barrel was marked Ancient Age (in reference to the distillery, not necessarily for the brand). Likewise, the barrels that are marked Old Fitzgerald have been used for Weller and Van Winkle bourbons.
As far as I know, and I will confirm this with Harlen, all BT Mash bill #1 is entered into the barrel at the same proof (likewise for the other Mash bills).
Finally, our wheated bourbons are entered into the barrel at significantly lower proof than the rye recipe mash bills.