If you've still got the build sticker in the boot, it will be stuck on the reverse of the rear panel. And is usual stuck on upside down so you can read it when you lean into the boot.
The same sticker was also stuck to the service book, if you have this it's often easier to read as it will have been kept clean and in good condition inside the document wallet.
The sticker gives lots of useful information about the original factory spec of the car, including the list of options and any extras that may have been ordered at point of sale.
It will show:
The full VIN (Here's how to read the VIN (https://www.vwgolfmk2.co.uk/clubforum/index.php?topic=19.new#new))
Type
Engine and gearbox codes
Paint code
Upholstery code
and option list
Here's how to read it:
(https://eddypeck.files.wordpress.com/2017/07/bootsticker_zpswfjvgtp4.jpg)
And this little gem will decode the options for you:
http://igorweb.org/equidec.aspx
List of many options here: https://www.vwgolfmk2.co.uk/clubforum/index.php?topic=45.0