Neptune Compacto Pen

Can anyone help me with this old white metal dip pen I recently acquired at an auction?
It is engrave Neptune Compacto. It was in a c1930s wooden box with various calligraphy pens. I’ve Google searched but unable to find any info.
Many thanks

 

If you move the button back in that slot, does the nib section retract into the body? Looks like it would. I can see the silhouette of the button to the right where it would lock it in the retracted position.

 

Looks like you're missing the cap:

https://www.worthpoint.com/worthopedia/neptune-compacto-stylographic-pen-453848509

 

Yes, the nib does retract. Unfortunately there is no top.

 

Is it a fountain (rather than dip) pen?
I know nothing of old pens and am just trying to figure it out.

 

Its definitely a dip pin. Thanks for taking the time to look at it!

 

Thank you!