PS Form 1508 at a glance
What it is: PS Form 1508 is the Statement by Shipper of Firearms (Domestic Mail Manual C024, retain form for 1 year).
Who signs: Sign under By (Signature and Title).
This form can only be used by manufacturers or dealers of firearms.
A filled-in PS Form 1508 example: a dealer mails parcels

How to fill out PS Form 1508, box by box
Addresses on Parcels
More rules for PS Form 1508
The undersigned is a manufacturer of firearms or bona fide dealer therein, and the parcels presented for mailing herewith are customary trade shipments or other articles for repair or replacement of parts. To the best of my knowledge and belief, the addresses are manufacturers of firearms or bona fide dealers therein.
Sources
[1] PS Form 1508 (April, 1994), Statement by Shipper of Firearms, U.S. Postal Service (the Official source link on this page).



