Searching for "dsi east rochester ny" got me this:
Despatch Shops Inc.
Thanks very much, that link shows:
DSI was a subsidiary of New York Central located in East Rochester, NY. The company was passed on to Penn Central, and ceased freight car production in 1970.
I guess DSI stood for "Despatch Shops Incorporated". Perhaps the "DSI Inc" stencil shown above is an error of redundancy. The shops were down the tracks and to the left in this 2011 photo, taken from behind the former Despatch Junction hobby shop which burned down a couple years ago but has since been rebuilt. (Yes, the names are "Despatch" not "Dispatch".)
Used to be four main tracks until CTC installation in 1957. I remember two main tracks and a third track for locals in the 1960's. Look close at the second photo and you can see a signal bridge and crossovers in the distance, not far from where I lived as a kid.
former Despatch Shops site at East Rochester
Google imagery shows remnants of the third track and a switch leading to where the shops used to be. A large building nearby for "Sentry Safe" is maybe made over from one of the old car shop buildings?