Hey there, I'm looking to get my hands on some 27'' tyres for a pair of old Mavic e2 rims. Thing is, I'm not quite getting the sizing. The rims appear to have an inside diameter of 19mm so I thought I was looking to get 23mm tyres! However i was terribly confused to find 27'' tyres come in

27 x 1 1/4
27 x 1 1/8
27 x 1

Which of these do you think would be the equivalent of 23mm tyres?

Cheers, and thanks a mill in advance. I'm very sorry if this has been asked a hundred times before, it's quite tricky to use the search for specific numerical sizes!