Where from?

Wondering how these are attached to the bracelet...

 

My error, you're right, I thought iron was involved in the making, as in Tsuba part of the Japanese sword!
Question is still how would wood stand with soldering...

 

I would be very surprised if this were bog oak. It could have been an old menuki attached somehow to a sterling pin.

Yes, shakudo is a copper and gold alloy. Menuki were made of different metals, depending on how much money the owner was able to spend, but mostly shakudo. Some were silver or gold.

Someone who is used to delicate soldering can solder a shakudo menuki to another material. It could also have been attached another way.

 

Authentic menuki are made with a repossee process with the added "gold" etc. done with Zogan inlay/damascene process. The bracelet above appears to be cast pieces with a patina and electroplated gold.

 

Scratches show silver under the brown

 

"Shibuichi is primarily copper and silver in varying proportions, again dependant on the color desired. The silver percentage can range from 2% to 60% or more, but more often would fall in the 15 to 40% range. These percentages are not haphazard, but are calculated for a specific color result based on centuries of experience. Shibuichi patinated with the traditional Japanese irotsuke technique offers a wide range of grays with some browns when using very low silver content. Pure gold and silver are not affected by the irotsuke chemical patination so retain their natural raw colors."