SUNOBE blade (Non-traditional Japanese sword)
There are Japanese blades made from modern steel in 20th century. Most of them are in the military mount. They are called "SUNOBE blades".
They don't have any layer pattern, and the steel colour is different to traditional swords. The hamon area is black like a mirror, and the remain surface is misty dark. No effect of steel particles. Because the quality of the steel is same as cheep as the material.
This kind of blade is not an object to be appreciated as art. It is just a weapon or an antique. We have to distinguish between traditional Japanese blade and SUNOBE.
"SUNOBE blade"
This is a military sword in 20th century.

Another example of "SUNOBE blade"
This is a souvenir from the early 20th century or the end of 19th century. It should be called knife rather than "tanto".

In primary meaning, the word "SUNOBE" describes the process of drawing out the steel block to the length of the blade. The naming for such blade comes from its easy process of making, because the blade was made up without fold welding work. For modern steel such process is not necessary.
In Japanese market, a price of SUNOBE is far lower than real blade's. Therefor some kind of dealers confuse beginners between sunobe blades and traditional blades.
Usually we use the word "SUNOBE" for all blades made of modern steel. But in exact meaning, it should be used to the blade made from one block of modern steel without fold welding.
In fact, there are various kinds of non-traditional blades in Japanese style.
Other words around Traditional and Non-traditional Japanese swords.
There are many words to confuse sword collectors. Some dealers are using such words as they like.
SHOWA-TO, this word is used as same meaning of "SUNOBE". The direct meaning of "Showa-to" is "blade in Showa era". So this word makes beginners confuse to "All blades in Showa era are non-traditional".
GUNTO, "Gun-to" means "military swords". This word can be used for the same meaning of Showa-to, because most of "Gun-to" were sunobe blade. But some officers put really good traditional blade into their military mount.
MURATA-TO, a sunobe blade in Meiji period.
TANREN-TO, "Tanren" means fold welding in this case, and this word was used as traditional Japanese sword to distinguish it from non-traditional Japanese swords. But this word can't distinguish the swords what fold welded with modern steel. A layer pattern is not the proof of traditional Japanese sword.
HAN-TAN-TO, it means "half" tanren-to. It doesn't make sense, but old dealers like to use this word. The real meaning of this word is, a blade made with non-folded modern steel, but using several kinds of steels to construct it.
MANTETSU-TO, a kind of blades what a Japanese company made in Manchuria in WWII. It is constructed with modern steels those are hard steel pipe and mild steel core.
NIHON-TO/NIPPON-TO, Nihon or Nippon means Japan. So it should be used only for traditional Japanese swords. But sometimes it is used as the meaning of Japanese style sword.

SHIN-NIHONTO, "Shin" means new, so it means "new Japanese sword". It is a kind of blade constructed with several kinds of modern steels. But I don't know exactly.
SPRING-TO, it is a modern steel blade tempered like spring, no hamon. Usually it is plated with chrome and a hamon-like pattern is put on it by polishing.
JAPANESE SWORD/JAPANESE BLADE, we use this word as the meaning of traditional Japanese sword, but some people think it as the sword made in Japan. It may be not wrong. We can't help the confusion.
One example of close-up picture.
This sunobe blade is well polished by the modern style.
It is made of non folded modern steel. The grain on the surface is not made of particles. It is made of full of small dimples. There is no particles on the steel surface. So the steel is not bright, it is dark and misty colour.
In the exact meaning, this is not a sunobe, because there are different steel (mild) on the shinogiji. It should be called Han-Tan-To.

For advanced persons
Today in 21st century, there are some strange Japanese styled swords that have a visible layer pattern and a strange steel colour. The steel is made by the fold welding method using some different kinds of modern steel.
The worth of such blade is same to a SUNOBE blade. Any layer pattern designs have no meaning for steel quality.
For modern steel, fold welding work has no effect onto its quality. The layer pattern design is only interesting for eyes.
To well recognize the colour and the particles of steel is very important to appreciate Japanese blades. ( => steel )
But I am afraid that in the future it will become difficult to distinguish the traditional Japanese blade from the others.
In Japan, sunobe blades are illegal. We can't have such blades. Japanese citizen never have any weapons.
Japanese style sword that made of modern steel is also illegal, even if it has pattern welding.
Only blades made of traditional method and material can be recognized as cultural assets. The educational office put a registration card to prove it as cultural asset. Japanese citizen can have swords only as cultural asset. Blades what can't get the card are disposed by the police.
Never try to bring such illegal sword into Japan.