Absolutely gorgeous pieces. I was offered "Girl and the Dove" for $2000 last weekend and I said, "No." I should have risked divorce.
The Kraka pieces designed in 1957 were numbered 358-363. The number on your piece seems to be 347, from what I can see, which was 1955. The question on this piece is about the "PU" before the number (P=Palmqvist; U=handformed) as this code was only used after 1960 on serial production pieces. Not that it matters much, as it's a gorgeous piece.
The Ariel pieces are harder to date. According to the Orrefors book edited by Wickman, the early numbers for Ariel don't reliably give a date. I'd think the design of your piece dates to the early 1940's. It's not the same design as the the one you show in the link. It's also possible that your piece was produced in 1972 when Orrefors reintroduced some of Ohstrom's earlier designs. It's not clear to me that the Ariel items with the suffix G produced in 1958 were new designs or old designs.
What is clear, though, is that it's a wonderful piece. If Bill Geary or Daniel S are around, either of them could clear up the production dates, I'm sure.