I looked at the Egg myself ( Satruday a week ago) and asked the owner about the caliber. He said he was not certain that it was 450/400. (Sorta nice to see an english double rife, a pretty high grade Darne and a Hubertus stalking rifle at the Jackson, MS gun show.) Needless to say the EGG needs a chamber cast and bore slug....but guessing on the weight of the gun......if it is a 450/400 , it might be the short 450/400 (2 3/8")???? The short ones do go back to 1880. I hope not! I would bet the ranch it is one of the Henry Eggs that was listed on SoldUSA. Compare the photos of the one that sold in the $4,500 range. Note the other EGG listed at the same time was supposed to be 450 bpe 3 1/4 (I think) and its auction estimate was astronomical. Whoever gets the chamber cast...please post. it would be interesting to really know.....!!!