Welcome to the Forum and congrats on the new to you Redwood. Most likely the grate is rusty from use and the loss of the porcelain on the cooktop grate. Lift the lid off of the cooktop and confirm the make and model number. Probably an Atwood range. Google the model for a parts diagram and then google shop and locate your new grate. Shouldn't be too expensive and will look a lot better.
Chris & Maria
2012 36RL, Full Body Paint, Dual Awning, Dual a/c, Splendide Combo, Fisher Paykel dishwasher, 6.5kW Onan, Goodyear G614's. 2015 F550 6.7l, 4X4, Lariat, CC, 176" WB, Long Box, B&W Companion