I have a lovely old Osmia Luxus I would like to get back to work. Making it a daily writer.
It has a push button filler which is leaking air if i blow true it and generally not working.

Any advice is welcome. I would like to disassemble it to see the internals but have no idea how to go about it safely.
As a craftsman i have plenty of experience working on fine mechanical items but I have no experience with fountain pens besides nib tuning. I am looking for someone with specific experience repairing Osmia pens to guide me true the process.

Thank you for your help.