Weddingbee boards

Hello bees -- now that I've got your attention, can you help me out to make sure that our save-the-date (and eventually invitation) gets where it's going?

The address we've been given (via text message, hence my typographical concern) reads something like the following:

1234 rear, sesame st.

Obviously they are in the rear apartment at 1234 Sesame Street. But where do I put the "Rear" in the address? Is it [1234 Rear Sesame Street] (which sounds to me like the street name is "Rear Sesame"), [1234 Sesame Street (Rear)], [1234 (Rear) Sesame Street], or some sort of variation that I haven't identified yet?

Thanks for any help that you can provide me!

Oh, do they live on one of those properties where there's a little house behind the main house, or something like that?  I have never heard of it being referred to as the "rear" in the address, though - usually it's 1234 A & B, or the back house has a completely different street number (so 1234 and 1236, for example).  I would ask for clarification - ask them exactly how it's written for post office purposes.

I googled and this is what came up as some example addresses:

Thanks for the advice, guys! I went with 1234 Sesame Street, Rear Apartment, and I'll have my FI check in with them to make sure they received the save-the-date. (They're his high school friends, otherwise I would have followed up myself before to clarify.) I even spent time on Google Maps street view trying to see whether there was a tiny house or just a back entrance or whatever! Oh, mailings...