As any treasure map, The Michael Rosen Map is Rectangular, around 25x40 cm and weighs very little. Michael Rosen stated in The Michael Rosen Map Trilogy that the map is made out of
Magic Plums. Well, actually, it was made out of paper.
As stated by Michael Rosen in the The Michael Rosen Map Trilogy, once you own The Michael Rosen Map, you have to go to The Island of the Plums. There, you can find Magic Plums, Which grant you many powers such as immortality, super strength and returning physical forms. That's why The Harrybo Company desires to go there, to become the ultimate power.
The first known owner is the shopowner of the Samons The Iron Toenail Shop, where Michael Rosen first discovered the Michael Rosen Map. The shopowner was later killed by a passing speed train. The ownership now moved from him to Michael Rosen. After a lot of adventure, Michael Rosen lost the map. He searched The Island of the Plums for it, but nothing... At the end of The Michael Rosen Map Trilogy, George takes it out of his pocket, along with three Magic Plums.