This is the link to Brownings website on the Auto 5's ...for serial numbers...
Date Historic Information Serial Number Info
1903-1939 First 10,000 shipped to U.S. Marked with "BROWNING AUTOMATIC ARMS CO. OGDEN UTAH-U.S.A." Very few serial number records remain. Beginning with Serial Number 1 to approximately 228,000. Exact production figures are not available. Year of manufacture on Pre-World War II production is strictly a guess.
1940-1946 From 1940 to 1946 production of the Auto-5 was turned over to Remington. Serial number is on the side of receiver. "ABC" for American made Version. (A=16 gauge, B-12 gauge, C=20 gauge) 1946+229,000-237,000
1947 237001-249000
1948 249001-270000
1949 270001-285000
1950 285001-315000
1951 315001-346000
1952 F.N. took over production of the Auto-5. 346001-387000
1953
Note: ( and the list goes on / I only copied a portion of it here ...)
looks like it indicates the age is between 1903 - 1939 with nothing more definite. I don't know anything about the X either ...but it would be an A, B, or C if was a gun made after 1946 but those serial numbers start at 229000 which is much higher than your 26,032 ....