Decoding your fender tag shows the following.
RM23:
Plymouth Belvedere,Satellite
Medium, Road Runner
2 Door Hardtop
H9E: 383 330HP OR 335HP 1-4BBL 8 CYL
1969
Los Angeles, CA, USA
168259: Sequence number
E63: 383 cid 4 barrel V8 High Performance
D21: 4 Speed Manual Transmission
B5: Bright Blue Metallic (Dodge), Blue Fire Metallic (Plymouth) Exterior Color
H2B: Trim - High, Vinyl Bench Seat, Blue
B7: Medium Blue Metallic (Dodge), Jamaica Blue Metallic (Plymouth), Jubilee Blue Metallic (Chrysler) Int. Door Frames
703: Build Date: July 03
486217: Order number
B5: Bright Blue Metallic (Dodge), Blue Fire Metallic (Plymouth) Top Color
A01: Light Package
G33: LH Remote Racing Mirror
L31: Hood/Fender Mounted Turn Signals
M21: Roof drip rail moldings
R11: Radio Solid State AM (2 Watts)
END: End of Sales Codes
So it was built on July 03. Hope this helps.
There is also a number stamped on the "K" member that should confirm this. Also look at the right side of the engine, You'll find the production (casting) date. I hope this helps, Welcome to the group.
Dan