63 is the year of design and 173 indicates that this is is the 173rd of Lundin's Expo designs in this sequence, which started in 1958. Lundin's Expo series started in 1953, and restarted at number 1 three times. She made a total of roughly 736 Expo pieces, some of which were very limited runs and some of which were made over a number of years. I know this doesn't help you too much with the possible value of this piece, but it gives you a context, I hope.
Without seeing a close up of the piece, hard to tell what technique has been used. Looks more like Graal and definitely not Ariel, but the walls are much thinner than her standard Graal pieces. Also, I wonder why it would have an Expo number rather than a Graal number.
Looks like a lovely piece, as most of Lundin's pieces are.
Good luck whatever you decide to do.