I have read a lot about date codes and why imprints are stamped heavier or lighter, smaller or bigger, or is it the correct date code for the period of manufacture. All I can say is it was a business making a product. Sometimes things were missed, went unnoticed, quality dropped to get product out the door. If you see a stamp which isn’t very crisp / clear, it’s because the tungsten carbide stamp (see photos below) that produces the imprint on the cap is worn out and needs replacing. Some times production carried on before it was noticed. Sometimes production were under pressure to get units assembled and out the door. Some times there were no spare date code stamps and had to make do. Sometimes the wrong date code stamp was used and units were going out with the incorrect date code, nothing wrong with the pen itself, just the wrong date code. So although a majority of the time they were correct, like any other collectables, anomalies crop up, odd mistakes were made.
Dating your pen should be easy by following the table below.
Parker's started manufacturing Parker 25's in 1975. There appears to be some uncertainty on the internet when they stopped. I actually have some stamped IIIN and IIN. I remember aquiring them, these would be the first and second quarter in 1999.To date I have not seen any later than this. I also have the Parker Staff Cash Sales Price List from 28/11/99 showing the P25 still for sale.
To find a 25 without a stamp is very rare. I've only seen two and I have one. When I say no stamp, I mean no PARKER, no logo, no date code, nothing.
Below: A tungsten carbide date code stamp. I cannot remember exactly which model pen it is for, maybe a Relex, but the principle is the same. The top greyer carbide part which has the ‘PARKER’ logo and date code is brazed onto a ground tool steel holder. It is then spark eroded with a ‘female’ shape copper electrode which has been machined on a CNC milling machine. This produces a 'male' shape when spark eroded into the carbide. This particular one does not have a date code, just the logo and PARKER stamp.
Look closely; notice how it is a mirror image i.e. 'logo REKRAP 'in reverse, which will stamp 'PARKER logo'. This is so when the impression is stamped on the pen it reads the right way round. These were very time consuming to manufacture due to all the different operations and costly.
It's worth pointing out a quality procedure which had to be followed was the stamp was suppose to align with the clip i.e. the end of the clip should sit between the A and the R of PARKER. Although that is not to say many were slightly off but still acceptable.