Interesting precancel. I have a number of them, too, but never much looked at whether or not they are only initials or if they contain a full company name on them (I'll have to give them another look.)
As I understand it, the post office requirement for dated precancels merely required that the company affix their name (initials) and month/year to the stamp, so I suppose the number of rubber stamps made for the purpose could be quite large.
Back to Idealite, did you know they were a manufacturer of lamp shades? Here's a picture of the company in Jersey City from the 1920's or 1930's...(I love that Railway Express truck!):
