Literally, serba satu means one of each (type). If I'm not mistaken, serba satu means more than just jewellery. "Hantaran serba satu" are the gifts from the groom to the bride. It can include one change of clothing, one pair of shoes, one jewellery set as Ramona mentioned, one cosmetics set, and etc. "Hantaran serba dua" means the bride gets two of each (type of gift). This means, two changes of clothing, two pairs of shoes, etc.
Traditionally, an odd number of hantaran is presented (7, 9, 11).

In the case you mentioned, the bride received a ring plus one of each type of gift. Couldn't find a specific source about this, but take a look at the ones below. Hope this helps.

http://www.proz.com/kudoz/malay_to_english...serba_satu.html