How is pewter made?
When making pewter the tin is first melted in a pot that is called a crucible. After the tin is liquefied the copper and antimony are added. Up to 3 percent of the mixture will be copper, and 2 to 8 percent of the mixture will be antimony. The antimony and copper dissolve in the liquefied tin, and the mixture is blended thoroughly. The hot mixture is then poured into molds, which might be made from plaster, metal or wood.
Unfortunately, Pewter is a common name describing several very similar metal alloys. It is important to know if it is lead-pewter (the kind the Romans used to use for drinking--causing madness; this is till used for small statues, trinkets, etc.) or silver-pewter or tin-pewter (the kind now often used in drinkware and jewellery). I would suspect it is silver-pewter and will be safe, but it is not necessarily wise to do so without checking.
Tin copper and lead were used to make pewter bowls, plates, etc. Common eating and serving ware were made of pewter. 85% tin, with less than 1% copper and other materials for hardness. Lead was added in cheaper versions that were not used for food. Lead is no longer allowed in pewter because of toxicity. Pewter has been largely replaced by glass.