It really is fun that I can tell a difference! When we got our first two eggs in two days we assumed they were from the same girl but obviously couldn't be certain... We were actually assuming it was our barred rock just from the one observation that she is a slightly bigger girl than our RIR...
Our RIR started laying recently and I'm surprised at how frequent her laying has been! We only have three girls: one RIR, one barred rock and an EE.
Our EE hasn't started laying yet and it's obvious to tell the difference between the RIR and barred rock eggs because the RIR lays a darker tan...