Hi Vicky
It is entirely up to you if you and include it and where you might include it. Technically you don't need to include the word vintage in any of your titles as it is a given your items are vintage from the category you chose and this is embedded in the html.
However from the point of view of the buyer it is helpful to see that word so they can instantly tell that the item is vintage when a thumbnail is in front of them. For SEO purposes your most important keywords should fit into the url as this is the most searchable part of information. So from that perspective and that of the buyer, the beginning is therefore the best placement should you decide to include it.
Claire
Team Leader