Paul,
The tool has 15 stamped on the side and the bell piece is threaded on the inside and has 15 stamped on it. The little pieces (5 each size) are stamped 968 and 107. Each of the ring pieces has different sizes (some too faint to really read), but numbers like 2 3/4, 2 5/8, 2 7/8, 2 1/4...