I've got a fair bit of Orrefors and it's all marked. Generally, I will buy unmarked pieces that I like but none have them have turned out be Orrefors. I think that the lobed vase well might be Swedish. In terms of buying the other piece, it might only be marked 'Of' and numbers. But, if you look at other threads on here, you'll find very nice engraved pieces that aren't marked and aren't Orrefors, particularly little birds. For me, it's if I like it, and how much I'm willing to pay for it. For example, I'd buy the lobed piece as I like the style and I haven't seen one like it before, but I'd limit my offer to the lower middle of my spending range.
PS Sorry Nic, I keep giving you a "k" at the end of your name.