The official age is 5 yrs, but it does have good value nonetheless. My advice would be to email http://www.whiskyauction.com
and ask. The gentleman there is quite learned in the field of whiskey collection.
With regard to Stitzel-Weller, it was closed in 1991 when UDV purchased it. However, the recipes used at that distillery were continually made at the Bernheim distillery until 1999, when UDV relenquished its Bourbon holdings in Kentucky. All recipes and standing stock were sold to Sazerac Company (Buffalo Trace) with the exception of Old Fitzgerald and the Bernheim distillery, which were sold to Heaven Hill.
I saw a similar bottling sell for around 100 bucks for a pint, so you could guesstimate that if the label is intact and most of the whiskey is in the bottle with an unbroken seal, it would fetch anywhere from 50-150 US dollars to the right collector.