Postcard: Wow, Look At This Old Train

For those who didn’t know the M train made an appearance on our train tracks, this picture proves it.

Info from the eBay seller says that this train is southbound from Kings Highway on October 23, 2004, which is not that long ago.  When looking at this picture, it seems like this train was from decades ago.

If this picture is from 2004, was this vintage looking M train on our track simply a MTA glitch or was there a reason for this?