This machine is not a BX, but a B. It also appears to have originally been sold as a $10.00 Eagle (without the case), and the $2.00 case, available separately, was later added. This is a scarce configuration, as the vast majority of Eagles were sold with cases (for $12.00).
Eagles with serial numbers below about 146,000
never had mandrel tags. Many collectors mistakenly add these to early production machines, but it's the mark of later diddling.
As for dating, the numbers stamped on the rear edge of the metal base will be the serial number, and these started at 80,000. This machine will number somewhere between 80,000 and approx. 146,000. 80,000 was manufactured around August 1897, and No.146,000 was reached about a year later.
All this information, photos, and much more was published recently in
The Antique Phonograph.
George P.