Yup, of course Type 53s are another subject. But their numbering scheme evolved over time with the transition from the 296 to the 26 designation for Jianshe Arsenal.
--The 296 rifles had a year, a period, and a month.
--The trials rifles produced in December 1953 had an A and up to 5 digits
--The 296 rifles used a simple serialization starting with a 1 in the "millions" place, presumably 1000001, while Jianshe was called 296 that continued into 1955.
--Later in 1955 they changed to Factory 26 and with that they began using the year of production code in the "millions" place, in other words 3 for 3rd year of production in 1955, and 4 for 4th year of production in 1956
--No known production from 1957-59
--In 1960 they switched to the single letter block with a four digit serial number, similar to the 1959-60 Type 56 SKSs.
Yours is a good example of an early 1955 (February), whereas my example is later in 1955 after the change from 296 to 26.