One more try - Can you ID this S-100 Serial board?

[Tothwolf]

On Wed, 30 Sep 2015, jwsmobile wrote:

> I couldn't spot how they did level shifting to RS232 levels.  The SI 
> signal appears to go to a 7400 next to one of the Uarts.
>
> One of the Uarts is one which requires it would seem 12 v as well, but 
> it doesn't do the levels for rs232 (AY-3-1015)
>
> I'd need sharper images and possession of the board to peer at it for an 
> hour or so to try to figure it out.
>
> Also the edge card space from the dual 50 pin headers seem to be 
> suspicious. i don't have an S100 spec to look at handy, but I was going 
> to see if there is any decoding going on, or maybe this is just a buffer 
> board to go to another system.  There seems to be a lot of LS244 and so 
> forth going on on the way to the edge card connectors, which smells more 
> like a buffer board than a serial board.  that is is not populated but 
> for the two 10 pin connectors is more interesting.
>
> Maybe someone else will figure out more or know more.

The resistor networks connected to those traces are also not populated.

Wonder what the deal is with the missing C2 right next to the crystal 
though? Broken off?