Here are a list of treasures you can combine with each other to sell them for more than you could get for them individually:
Beerstein + Red Catseye + Green Catseye + Yellow Catseye = 20,000 pasentas.
Elegent Mask + Red Gem + Purple Gem + Green Gem = 30,000 pasentas (I think, not entirely sure about this one)
Butterfly Lamp + Red Eye + Green Eye + Blue Eye = 32,000 pasentas.
Crown + Crown Jewel + Royal Insignia = Salazar Family Crown = 48,000 pasentas.
Golden Lynx + Red Stone of Faith + Green Stone of Judgement + Blue Stone of treason = 40,000 pasentas.
The Crown Jewel can only be obtained by killing Salazar's Assisstant in the sewers.
You can find two Butterfly Lamps and at least two of each colour eyes.
You can find two Elegant Masks (one in the Village and on in the Castle) but you can only find one of each gem.
These are all the treasures that combine, there are no others.
Added by: nintendo_dude Sep 19th 2006, ID#6745