So... the markings are not totally useless to the avid drinker or collector, but you do need some inside information to glean anything of use regarding production dates...
For example, Maker's Mark bottles over the years have been made by at least Pierce, Ball, and Anchor ... and I think Owens, too. If you knew the transfer dates, you could look at the markings and determine not-earlier-than, and not-later-than ... bottling dates. And if you know which mark is for the drawings year ... you can always determine a not-earlier-than bottling date.
Otherwise, to the average Joe, the raised glass markings on teh bottom of thebottle are meaningless.
You could also date the bottlings by looking at the lot code ... if you could find and decipher it ... it always contains the bottling date, too ... frequently down to the minute. It is usually found on the back of the bottle near the bottom and is either laser etched or ink jet printed. These have been on most spirit bottles since the mid to late 1990's. The code is usually around 13 or so characters ... usually starts with the letter L (for Lot) ... and is a mix of letters and numbers. Buried in there is the bottling date ... written in a 4 or 5 digit Julien format ... for example today would be 9143 or 09143 ... (being the 143rd day of 2009)