Thank you kindly

This is possibly a newbie question, but I'm honestly unsure. If I clean my older coins will they decrease in value?..

I'm super new to this, please bare with me. i've got what appears to be the same size, weight, and i'm assuming material as a penny.. only it's pressed with the canadian nickel design. I've had it for some time now, just thought it was neat. I hope the attachments work,. Any info would be great! (Wo...