parker 51 Which year was this Parker 51 nib made

[Alienorange]

Please help me identify the code on this Parker 51 nib. It only says “1” instead of an accurate year number, and I can’t find any similar nib online, or any relevant information. I’m not perfectly sure if it’s a 51 nib, however, other than the year code, everything else matches the 51 nib. The code also says “PARKER”, “RU-PL” and “MADE IN USA”.

[mitto]

Later production 51 nibs were not date coded. Don't know, however, what the 'I' means. 

[Mr.Rene]

Try: https://parker51.com/

maybe he knows...regards