If the full SN off the bottom of the grip frame is 636xx, you have a fairly early production .38 Military & Police, from about 1905. Finding a new hammer will be more difficult than for a newer version of this gun but not impossible. If you can post photos of the gun and a close-up of the hammer that would be helpful. At the bottom of the posts, click Post Reply then under Additional Options click Manage Attachments. You can post photos from there.