Decoding Gold Ring Hallmarks: Understanding '18CT', 'APTE', and 'PLAT'

Question
Good morning,
I have recently acquired a second hand ring(in Australia), made ~1950. It appears to be 18ct gold with another metal (platinum?)"bonded" on top of the gold band forming the setting for a single diamond (0.25-0.33ct)with a diamond chip set on either side. There are a few marks stamped on the inside of the ring, and I was wondering if you could confirm what they indicate. The marks are: "18CT", and next to that "APTE". On the other side of the setting is "PLAT".
Thanks for your time.

Answer
G'day Peter and many thanks for your query

You sound as though you have a classic design from the 50's and you have basically answered the question yourself.

The 18CT is for 18 carat gold and the PLAT is indeed for Platinum which they used either as an overlay band or in the white settings and shoulders so as NOT to throw the yellow gold colour into the diamond (Diamonds are graded by their LACK of yellow tint).

The other hallmark APTE is simply a Maker's Mark or design or even a Store name - but doesn't have any significance as to value. It's just for identification but it's good to record it anyway.

You might like to add this question to my blog at: http://how2valuejewelry.com/ and let others read about it. Who knows - someone from the original factory might just answer.

Hope this helps