The lowest serial number I've recorded with the ILION, N.Y. on the watertable and no rib legend is 241182 --
241182 01 VHE, 16-gauge, 26-inch.jpeg
241182 06 no rib legend.jpeg
As far as I've found they only produced the late PARKER ILION, N.Y. grip cap in the size for 1-frame and larger stocks --
241685 02 PARKER ILION, N.Y..JPG
and they only begin appearing about 500 guns later. The PARKER BROS. MERIDEN, CONN. grip caps appear on the 0-frame and smaller to the end.