From 1898 some locos were rebuilt with  pressure boilers thus when an additional ten T26s (numbers 1250–1259) were built in 1902 these were fitted with the new boilers as standard.
Starting in 1898, some locomotives were modified to include pressure boilers. When ten more T26s (numbers 1250–1259) were built in 1902, they received the new boiler design as a standard feature.