Hi SueBru,
This is a curly one, alright! Given that you said it's base colour looks gold, and the odd marks on it, I'd say it's either EPNS or it could also be EPCA (Electro Plated Copper Alloy). This Makers mark (GS) is not easy to find in an Electroplaters Makers list, as most of them deal in EPNS (Elecro Plated Nickel Silver), and I'm sure this is EPNS. And a lot of them simply weren't registered at all.
Also, given those marks are so "odd", I'd say it's not from the UK. And I'd also say it probably wasn't officially assayed to record them, so very hard to find!
Maybe try around the Scandinavian countries, because they look a bit like rune symbols to me (or someone just made them up and could be Australian that wasn't officially recorded here!). Although I read about a guy called George Savage who used GS and "English Hallmark likenesses". But I don't know if I'd call them likenesses, since they're so unusual! There were no pictures, unfortunately, but possibly him... He was from Canada.
And just a quick FYI to anyone reading this, the word HALLMARK is only applied to platinum, palladium, silver and gold articles that have been sent to an assay office. It was originally called "the Hall" from the ancient Goldsmiths Company's hall where the first assay office was set up in 1478 in London. The 'hall' would assay, test and record their precious metal content, (which must have a certain weight included in it to be hallmarked, as they are often alloyed with other metals for strengthening), and then gave them their hallmark. By law, in many countries (not all), they must be hallmarked if being advertised for sale as gold, silver etc.
Others that are not officially assayed as one of the four precious metals, just have what is called a "MARK".
So being electroplated, this spoon has 'marks' on it, not 'hallmarks'.
This may help you when searching Google - don't ask for "hallmarks" - ask for electroplaters' "makers marks".
Unfortunately they are not as well documented as Hallmarks, if at all, so this will make it a tough task for you to find out who made that spoon.
But good luck - I love this kind of research too!
Cheers,
Megsy