Logbook an certificates

Hi all I've been trying to find out more about what I thought was my 1980 Mk1 Golf gls ( according to logbook)
So I sent off for a birth certificate from vw an it came back with some helpful things but I'm now confused.
The certificate says 1980 gl not gls
It's correct colour same vin on all papers. 
It also has interior colour listed an it list some m-codes an says about m-package if anybody could help me with where to find them that be great. 
Thanks 

The GL/GLS may vary between countries? ie a german GL spec may be badged as a GLS in UK and lots were taxfree imports back in the day so ended up UK registered but were wierd continental colour combinations and specifcations.

Loads on google about M code etc

https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=bodywork-fittings-and_2%2Foption-codes-that-can_2

Ok thanks for that 👍🏻
I'll look now about m codes