Shell pink dish with IRG unknown mark

I bought a box lot at an estate sale and i found this interested old dish in it. The only mark I see is IRG. I am having a very hard time finding anything about it. I love researching pottery and glass and this one is stumping me. I like this piece because it is a shell pink color and it can go with a lot of different things. I also like the shape. The dish measures 9 across by 7 wide. The back of the dish shows glazing, telling me it is rather old but I would love to know more. The only other thing I can tell you the box I purchased had several unique items like an old dresden platter, and another blueware platter that I may post later because I can barely read the mark (I cant really read it at all). Thanks!