いたろ, how?

[raikado]

I've come across this sentence in a manga:
ほら、大きい お姉さん 二人 いたろ？
Hora, ookii oneesan futari itaro?
It is translated as : There were two big girls, right?
The problem is いたろ, I don't understand how it is formed. I know it comes from いる and it seems to be some kind of assumption(kind of like だろう).

 

[Mike Cash]

いただろう

Your guess was almost there. Trust yourself a bit more.

 

[Toritoribe]

ろ is the shortened version of ろう, which is from a classical auxiliary verb. It's used only with the past form nowadays, thus, unlike いただろう, いるだろう doesn't change to いるろう.