This item needs repair but it has family history so I am hoping to get a wee bit more detail before trying to restore. I am assuming it is missing agate - it is tiny and clearly needs a good clean if nothing else. The pin also appears to be someone's handy work (not original) and the catch is gone. It has STG SIL on reverse so sterling silver and a very worn makers mark which I am going to assume the first initial is missing (almost see K or R but well worn) with the final initials being .H.L - essentially without the city assay I am unable to define a starting letter so hoping someone recognises the style and potential maker. My family has Scottish links but essentially the brooch could be from somewhere else. I would just like to have an idea which agate or agates it had so I can bring it back to life. Thanks in advance for your help. Hopefully with a maker I can research how it once looked. Regards Grid
The mark "STG SIL" is often an indication of a New Zealand or Australian origin. As you are in NZ you might like to have a trawl through one of these topics on Australian and New Zealand silversmiths to see if you come up with anything. Some of the images are missing but you might be able to match the initials with a bit of patience.
I think your L might actually be a Ltd for limited. I can find no evidence of any New Zealand firms using a Ltd though in Winsome Shepherds book of New Zealand Silversmiths and Goldsmiths. Nor can I find any makers with Kh or RH initials. It doesn't mean it's not from New Zealand though.