Just a few suggestions on where to go to find collections of sundials in Stockholm. One of the best collections is owned by the Royal Swedish Academy of Sciences. This collection is probably not on display for the public, but you could always try to get in touch with their Center for History of Science (+46 8 673 95 00) and ask them if they could show you the collection. It's mainly 18th century dials, but also a couple of nice 16th century dials, among them a diptych sun and moon dial from 1597 by Balthasaer Salibos.
Another good collection is owned by the Nordiska Museet, including three excellent sundials made by the Swedish instrumentmaker Philip Jacob Thelott around 1680. I would suggest that you get in touch with the museum in advance, I doubt that any of their sundials are on display. At the National Museum there are at least one or two sundials on display, and they have more in their collections. That's just a few suggestions, there are of course a lot more to see. Look at the walls of the churches and you will find a lot. One of the finest dials in the country is on top of the Anathomical Theatre in Uppsala (70 km north of Stockholm, 40 min by train). Take a look at it on their web-site; http://www.gustavianum.uu.se/english.htm Greetings Olle Amelin