"Juan" agrees to a simple contract with "Betty". This written contract has a single signature line at the end for the offeree. Juan has poor taste, so he "signs" it with a large wax seal of his own design.
Does the presence of a seal make the simple contract into a contract under seal?
EDIT: The jurisdiction is the United States of America.
While there may be an isolated holdout or two, almost no U.S. states make a distinction between contracts under seal and signed contracts. A seal is an acceptable substitute for a signature, as is any mark (such as an "X") intended as a signature by the person making it.
Many states require recorded documents to be notarized, which is a slightly different concept than the historical concept of a contract under seal. A document executed with your own seal is not a notarized contract.
As long as Juan used a personal seal, especially one that was registered to his name, then there is exactly one signature as far as most people in Japan are concerned: Juan signed the document properly. He could even have used a pen, but that would look silly to most Japanese people, especially if it was a contract for something important.
While a pen signature is technically acceptable and legally equivalent to seals and electronic seals, the Hanko/Inkan culture is very engrained. It is a result of the preference for seals that some institutions won't easily accept a pen signature unless you are a foreigner, and at least for some operations even request some kind of seal for such.
The most noticeable operation that almost always requires a seal would be to retrieve cash from your bank. Due to the contracts, a customer can't just write down their signature on withdrawal orders to the bank and instead needs to use a banking seal that they registered with their bankhouse.
As a result of seal culture, digital signatures for Japan almost always have a seal representation, even if it was only created digitally.
In england-and-wales, the Companies Act 2006 sets out provisions for when and how in the modern era documents may be “executed” such as equivalent to a company imprinting them with their seals.
As I recall back in the day it was largely the norm, but then became less necessary as signing was an adequate alternative, however it was still necessary to affix a seal to certain things, principally a deed. The difference between a contract and a deed is that a deed may be a unilateral promise and thus requires no consideration, yet if executed properly may still be binding.
In the modern day, section 44 Companies Act 2006 provides practical modern methods whereby companies may “execute” (rather than merely “sign“ documents, such as being signed by multiple officers or with witnesses.
