It was likely the shape of the briar block with which he worked that made him do it, but Paul chose to taper this chamber quite a bit. It is narrow at the bottom, but yes, a tamper head, such as that on an Atmos pipe nail, does fit flush on the bottom. Some people like their pipes to sit flat on their desk or work table, and this does just that, without requiring the support of the stem. That stem is acrylic, BTW and helps in providing a wide-open draw. The very light stain and uncoated bowl will assist in letting you get this wood dark and rich. New.
6” long, bowl 3.6” tall. Weight: 3.25 oz., 91 grams.