OK, looked at the schematic of the radio. It uses not only the old DIN, but also appears not to use modulator/audio output stage ground return in receive, so I would assume the radio does receive when there is no mic inserted. Am I correct?
Your radio connector is as follows...forget any chart you read for mic wiring because the mics assume you're wiring a stock, generic dpdt switch. I don't know what's inside your mic. Typically Japanese mics do have a DPDT switch with spring return connecting one side to the center pins on both sides. Most american made mics use spring copper leaf contacts with one pair open or closed for the mic and the another set that is normally closed to ground in rx and connected to the ptt line in transmit. Look inside and figure out what you have.
Since we both have Centurions, I already know that the mic is low impedance Dynamic around 500-600 ohms. Same as the old Realistic stock mics.
Internally, the schematic of the '453 shows pins 1 and 2 grounded, pin#3 is your PTT line, pin 4 is your mic audio, pin 5 is unconnected. In a typical electronic switched radio, pin 5 would have to be alternately grounded for ptt in transmit and modulator/spkr amp in receive. This radio doesn't require it from what the schematic shows.
So this seems simple
You're going to need to get a 5 pin 180 degree DIN plug. RS used to carry them. Yes, they are a pain to work on and best to have some heat shrink tubing. You need to be careful because the pins numbering is not sequential around the connector, so a good magnifying glass is necessary.
Connect the PTT and if there is a Shield on the mic to pin #1
Pin 2 can be left unconnected or treated as pin #1 too if there are both a ptt and shield and two don't fit on one pin.
Connect the PTT line on pin #3
Pin number 5 is unconnected.
Your best case is 3 connections like the courier phone plug. Same wire for PTT to pin 3 (center ring on courier phone plug probably red)
Same wire for mic audio (tip of phone plug and probably white) to pin 4
And same wire(s), probably black, for ground to pin 1 (Shaft if phone plug)
That should do. Probably better not to butcher the original mic. Most mic cords of the era had tinsel cord/ fabric entwined inside the conductor and near impossible to solder, so don't cut the cable or at least use desolder ends the original from the plug if you don't want this to turn into a nightmare. If you could find an in-line stereo phone jack, make an adapter instead.