Parker 180 Date

I see vintage Parker 180s listed on eBay with dates. I have a 180 fountain pen with the unique angled nib. It is all black matte finish. There is no identification or marking on it at all - anywhere. I have been all over it with a loupe. The only thing that IDs it as a Parker is the arrow clip. What am I missing?

The Parker 180 initially had no date code. The date code on these pens appeared in 1980. So if there is no date code then the pen is earlier (1977 to 1979).

Thanks, that clears it up.