Hi Alison,
I don't think this is Walther, though I could be wrong. I've owned a few of these in the past, both in amber & rauchtopas. They were certainly produced in the 30s as I have seen an example with a hallmarked silver rim - I can't remember the exact year but it was mid 1930s. Quality is very good, the examples I've handled have been satinised on the underside, then selectively polished. I've always thought these were French, quite possibly Verlys given the colours used & high standard of finish, but I don't have a complete Verlys France catalogue to check. Of course, there were many other makers of similar wares so it's likely to take a while to pin down.
Steven