How can I tell if my car has a closed deck engine by looking in the engine bay?

It's a version 2 gc8

Is there any codes or signs?

 

there is some cross hatch markings on the block by the crank sensor. Here's some good information http://www.scoobycity.co.uk/forums/f...-numbers-where

 

http://www.type-ra.com/what-model-is-my-impreza/

But if it's a MY 96 WRX then it's a normal block.

 

The only V2 car to have a CDB from the factory was the STI RA.

That's not saying your car doesn't have one as it could of had one fitted at some point in its life.
Easy way to tell, look at the block infront of the starter motor. If it has lines like in the pic below then it's a CDB.

 

https://www.scoobynet.com/wales-26/1025099-does-anyone-know-any-information-on-this-gc8.html

Here's the answer.

 

.....and the WRX RA.