Help required to identify a vintage IWC

Just dug this out from a pile of my Dad's stuff. For all the good of google... (and apart from making a trip down to the shops), I think here would be the best place to seek some advice on the model.

Definitely the place to come for vintage help and pointers.

Here is the first port of call in trying to establish which IWC you have : Which watch do I have?

By the way - it's a fantastic retro piece - excellent dial.

Thanks Mark. I tried looking through that wonderful collection of old catalogues but no joy. There was some online tool to roughly discern the year of production based on the caseback number, which seemed to indicate somewhere between 1976-1978, which is incidentally missing from the catalogue collection, talk about luck (or lack of it) :)