Saidan Mei Symbol on Tang

[protopheonix]

Anyone know what the symbol on the bottom of cutting test signatures are? I've been seeing them and couldn't find any information on what it is and am beyond curious. Most images will translate the kanji but not the symbol, so am looking to see what it stands for and the significance of it. Some pictures below (boxing the symbol)

 

1st image example:

 

 

2nd image example:

[Grey Doffin]

Hi Jack,

These are called Kao. They are personal seals.

Grey

[Bruce Pennington]

Jack,

Cutters, swordsmiths, tsuba craftsmen, even sayagaki writers (probably a word for that!) were known to use them.  Not all did, but some.  Like a personal trademark.  Some smith's used one that was hot-stamped into the nakago.  I have several of each type documented in the Stamps of the Japanese Sword document.

[SteveM]

Also politicians. They are still used today. Current Prime Minister's is on the far right.

 

 

 

Some more info

 

 

https://en.wikipedia.org/wiki/Huaya