The money will go Woking & Sam Beare Hospices as he again proves his commitment to the local community.
Dowson took the Cards to play-off glory in his first season at the Surrey club.
Now he will part with his reward for taking the club back up a year after their relegation.
The manager said: “I am delighted to give my winner’s medal, one of only 23 awarded, from the season to such a worthy and important cause as Woking & Sam Beare Hospices.
“I have come to learn a lot more about the charity and the great work they do over the last 6 months and it has really touched me.
“The care they provide for our local community is really amazing and if by donating my medal to be auctioned I can help them raise more invaluable funds then I will be very happy.
“The medal marks the achievements of the club over the season just past and I hope our supporters will want to get hold of this by bidding for it through this silent auction.”