An RF 500 is a listing in Topping's book of BC cancels. There was only 1 known copy of the cancel prior to this one showing up. Now there are 2 known copies. Straight line cancel Henrietta. 
The 90bs is cataloged as a booklet single (straight edge)Stamp printed between 1903 & 1908
For more information about the steamer, visit the Arrow Lakes Historical Society website (It's a very interesting story about Genelle Sawmill Co. )