Is it possible to use one of each

yes.

just to clarify, does it mean that i can put 1.0.3 + 1.0.4 for a total addition to block of 22%?

Yes
Legacy and non legacy count as different uniques.

There is more combos like that, people for example use two sojs for resources, or two zunimassa rings to get dual set combo (along with other different parts of both sets), +130 inteligence set bonus each.

This post was edited by ae1337 on Sep 2 2012 11:06am

Yes you can. I use both of the Sunkeepers on my Act 3 Frenzy barb and cut a ton of magic find from my other items lulz.

So max block is now:
Doombringer 7%
x2 Justice Lantern: 22%
Captain Crimson's Bowsprit:4%
StormShield: 34% (used it for ez calc)

64% block chance

not bad

I believe there's a cap for max block just like there is for frw

Yes you can dual equip them.

People are not too smart to lower the price of 03 lanterns.

I actually went out and bought one since the price went down.

Did you test this? (or have a source)

+ Helm of Command 8%
+ Barb Belt 5%