On IB's "Products and Exchanges" page (under "Resources"):
CME (GLOBEX) (2)
Futures:
G (5), L, m, s, SL, t
Order Legend
G = native GTC, g = simulated GTC, L = limit order, M = native market order, m = simulated market order, O = native MOO, LOO, MOC, LOC orders, o = simulated MOO, LOO...