What QSI board do I have?

It's not PS/1. What you have looks like the top two boards of an old QSI OEM three-board setup. The (missing) bottom board would be power supply and reverse. Check out a website called the Scaled Tin Rail. They may have a reference for your chip number. If you contact them, they can probably tell you exactly what you have. That site is under new management since the former owner died a year or so ago, so I don't know exactly what services they now offer, but the late Art Boynton was the QSI factory service rep. 

You shouldn't have a lot of trouble finding a bottom board to go with what you have. Those old systems don't sell for a lot of money. 

SH, the site is down, but I did find QS industries and shot them a mesage about this board.

So, is this the famous old "add on" sound for the old MTH engines that came without sounds?

I have a dead boarded MTH K-4 pensy that that would benefit possibly from this or my old MTH Nabisco 4-8-4 steamer that's only whistle- no chuff.

BTW- thanks for the direction! 

You have the top sound board and the middle power supply.  So all you need is the DCRU board.  No way to tell without listening now that TS web is down.  Speaker goes on the 2 pin prong by itself.  G

Thanks GGG, so I need an early "DCRU" board...right? I just want to search for one, correctly phrased.

Possible MTH availability or hit the bay?

Try putting an ad on the WTB board here on the Forum first. There's probably plenty of members who have DCRU boards left over from upgrades to TMCC or PS/2 and would sell them cheap. I probably have a couple laying around myself, but I don't have time to find them and take inventory just now. My "old parts" collection is a mess. I know where one is, but I also know it's fried, so that won't do you any good! 

Thanks SH, I just did that.