Yaesu uses a simple system in their serial so you can find out when the radio was made.
My FT 991A serial is 0E4600351
Clear it was made 2020 ( the 0 from the first number what gives the year of production)
E = March this year, January is starting offset with C...
460 is the batch number, 351 is the number of that batch.
Same goes for my FT 2000-D, Yaesu FT 100, or FT 847 with collins filters.
The FT 847 was made in 1998 first series, serial starting with 98.