Help with origin of SIRT caboose

http://www.rrpicturearchives.net/showPicture.aspx?id=820360
I know it was built by the Reading shops, they built these for the RDG, LV, and CNJ. Would anyone know the CR or previous number?

My guess is that's the same as SIRT #4 from back in the 70-80's.

Here is an earlier photo:
http://www.trainsarefun.com/protophotos/clifton.jpg

My notes say former RDG but that could be a guess.

Charles

Surpising it wasn't from B&O (SIRT was a B&O division).

The Caboose is an ex Philadelphia & Reading hack don't know the number

I think these cabooses were known as Northeastern cabooses,there was an two issue article about these cars in Railroad Model Craftsman "R M C" back in the 1980's...

Tom