Leather scabbards, without a wood core, had once a top coat of black lacquer.
On the Spanish Dragoon I just bought I observed remnants of a coat of about 2-3 mm thick.
This made the scabbard as stiff as a board. Over time the top coat gets busted and starts to crack. Moisture and dirt seeps in and pieces of the lacquer will drop off.
What we now wind up with are often totally dried up floppy leather scabbards with cracks etc.
The leather scabbards with a wooden core had also a top coat to keep the elements out.
This is also seen on steel scabbards with a leather outer casing.
The problem with all of the systems is A. the top coat has to be maintaned and B. and this refers to all scabbards, the blade should be clean and dry when sheated.
Cleaning the blade was no.1 with Katana. The blade never went back into the scabbard without a good wipe. Here in the West basically nobody cared much as all of the troopers sabres at least were made on the taxpayers dime and if something went wrong one just went to the armoury to get it fixed.
Most Gunto had a stainless blade, were purely ceremonial, as in just a reference to the warrior of old and had a thick steel scabbard with wood liners, the whole often in a canvas cover.
Gunto with a family blade had a wood liner that was more like an inner scabbard that fitted perfectly into the custom made steel scabbard and was easily removed to clean it from grit and dust.
Look at a leather scabbard from the 19th century. It often seems that the fittings are too large.
There are gaps between the leather and the brass. That's about how thick the top coat was.
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