I have in my possession some early postcards from Sweden. Early meaning 1901-1915.

They were part of a large collection I bought because I collect old Swedish town cancels.

Most of these items have good postal history value because of rare usages from small towns, and nice quality cancels.

For example, there's a 1906 card sent from the tiny Swedish island of Ven, postmarked at "SANKT IBB" which is a rare usage. That part of the "worth" I know.

But how does the 1906 colour postcard showing astronomer Tycho Brahe's research observatory compare, in terms of importance/value? I know very little about post cards, and their value.

Any comments and ideas would be appreciated.

Thanks in advance!
Peter