It's hit and miss with the signature requirement, but ALL International Registered Mail is treated as First Class in the US. The only Registered Mail that is accounted for every step of the way is Domestic. https://faq.usps.com/s/article/What-is-Registered-Mail-International
So my coin from Germany arrived today! The shipping estimate was 18 Jun. I expected it next month. Leave it to German efficiency to arrive a day early I present to you my Edward I Penny: Edward I Penny 1272-1307 Obverse: EDW REX ANGL DNS HYB Reverse: CIVI/TAS/LON/DON PS: I blame @Ryro for my recent kick on British hammered coins (all 3 that I now own haha)