HP-12C/12C platinum/15C CE date of manufacture

[Uwe-001]

My 3 modern made Voyager calculators have no serial no.

HP-12C,
2x CR2032, battery door with captive screw
KCC-REI-HPK-HSTNJ-KN11
RMN HSTNJ-KN11
L/NO. 9CJ251 (white glued label)

HP-12C platinum
2x CR2032, battery door with captive screw
KCC-REI-HPK-HSTNJ-KN11
RMN HSTNJ-KN11
L/NO. 9CJ310 (white glued label)

HP-15C CE
2x CR2032, battery door with captive screw
--
HSTNJ-KN13
L/NO. 9CJ323 (white glued label)
Collector's Edition No. 06506

Each is made in Philippines, as printed on the bottom of the device.

Is it possible to get some information about their date of manufacture? As far as i know the L/NO. is not a serial number.

Uwe