The Futaba's will also APPEAR to work properly but performance MAY suffer.

From Futaba's FAQ page:

Please explain Hi and Low band to me? I am not sure what the difference is between them.
Most of our 72MHz receivers are now tuned to the center of either a low band frequency (channel 11 to channel 35) or high band (channel 36 to channel 60).

By tuning to each band, you can easily and safely change your receiver crystal to anywhere within this high or low band range, without having to send it in to be retuned.

If you have a receiver that is not marked as to which channel it is, or if it is not marked with a sticker that says if it is High or Low, you can check inside the crystal slot to see if there is a red mark. If there is a red mark, this indicates that the receiver is High band.