Gas fire with rocks for 'real fire' look - used, old (Sharrow S7)

Black gas fire. It's an insert that you put into a wall with a flue. It has special rocks that look like coal so it burns a flame - so it looks like a real fire but without any ash etc. We never used it - it came with the house we bought 25 years ago. So no guarantee of it's functionality. The odd looking picture shows how deep it is.