The second item, with the swans, certainly looks like Mats Jonasson. He worked for Kosta from 1969-75, so that gives you a timeframe.
As to value, probably the best thing to do is watch Ebay. Mats Jonasson pieces turn up regularly, so search these for Kosta pieces - that'd be my advice.
Here's another piece of advice too.. :wink: Buy Ivo Haanstras book: Glass Fact File A-Z, published by Millers, ISBN 1 84000 429 0. It's an invaluable book and inexpensive to buy.