From what I remember, CaseIH has never "made" their own hay equipment. Prior to Fiat buying up New Holland (they already owned CaseIH), all the CaseIH hay tools were made by Heston (AGCO). Once Fiat had NH under it's wing, the CaseIH hay tools were basically repainted NH models.
From the pictures I looked at of a 8309 on tractorhouse, it seems like the 8309 is a repainted NH 411. I haven't had any experience with them, but they are an older machine. If it is in good shape, it would be a good mower for a smaller operation. As with all disc style mowers, make sure you check the cutterbar out.
Hope this helps, Josh