Very nice piece in decoration! Can you tell a little more on how it was found (location, had to dig it up, etc.)
I would suggest white metal/spelter or pewter. Definitely a decorative fluted bud base in appearance and detailed with scenes of Holland, etc. (Pewter that comes into contact with food is generally referred to as sadware. Pewter that doesn't come into contact with food or drink/consumption known as lay or "ley" pewter can have a lead content up to 15% with the rest of the tin and metals - thus it oxidizes more.)
The item needs a GENTLE cleaning to see if there are any marks/markings to identify the maker.
Oxidation on metal or pewter of course depends on what it has been subjected to over a period of time. You state you found it on a walk....so it was in the dirt, subjected to the elements, etc....and it has corroded.
Would suggest that you get a METAL POLISH/CLEANER (DO NOT use one for silver - it will ruin your piece for sure!) and see if it will help clean it up. Use a very soft cloth first then a soft brush!
