I recently picked up a second Siamese 98 Mauser, believe it is the 66 model and in 8x52R ? I had the type 45 which I believe is 8X50 R. Seems I've seen some place the main way to tell them apart is the T-45 has a raised peice of wood on the right side along the bolt and the T-66 doesn't ? Is this correct? Seems odd they would change calibers for such little difference ?