1. a professional appraiser, needs your location for suggestions or Google.
2. eBay watching.
The first will be best for insurance etc. The second will give you possible retail value but be aware subtle differences can impact rarity value. So a 6 inch model may have been produced by the hundred and sell for a few dollars, whereas, say, a 9 inch version only made in a handful could fetch hundreds of dollars. Variations can be in size, shape, colour, decoration and when made.
We can help to identify but buying a book on Blenko, I am sure a recommendation will follow and trawling other Blenko web sites will be quicker if it is a large collection,