The face of blades are the same to the sword mounts, but the confusion is a tachi blade in katana mount, or katana blade in tachi mount. To tell blades, we think as which it is made in original.
The obverse side of mounts
Tachi mount
It is hanged with cord cutting edge downward.
Katana mount
It is put into the waist sash cutting edge upward.
Wakizashi mount
Mounts for tanto blades
Aikuchi
Kaiken
Blades
Usually, there is a signature of the smith on the obverse side of the tang. If there are engravings in the blade, it on the obverse is main theme, on the reverse is secondary.
Tachi blade
Obverse
Katana and wakizashi blade
Obverse
In the case of shortened tachi blades, if it still has a signature on the tang, it is taken as tachi blade (suriage). If it is so much shortened as its signature cut off, it is taken as katana blade (O-suriage).
Katana (O-suriage tachi blade)
Obverse
This was tachi blade in its original. Then it was so shortened as the original tang doesn't exist. So it is taken as katana blade.
In a matter of fact, sometimes it appears an original unsigned blade that is difficult to tell tachi or katana.
Tanto blade
Obverse
Reverse
Naginata blade
The face is the same to tachi blade.
Obverse
When a naginata blade is shortened as O-suriage, it is taken as katana or wakizashi.
Wakizashi (O-suriage naginata blade)
Obverse
Yari
In the case of hira-sankaku-zukuri style, the ridge line side is obverse, and the flat side is reverse.
Yari (hira-sankaku-zukuri)
Obverse
Reverse
In the case of kanmuri-otoshi-zukuri (kikuchi-yari style), the face is the same to naginata.
Kikuchi-yari
Obverse
Tsurugi (ken)
The side which has signature is obverse. In the case of originally no signature, it is difficult to tell obverse/reverse.
Kogatana
It is bonded to handle (kozuka), and put into the kozuka slot on the reverse of scabbard, cutting edge upward.
The obverse of kogatana blade has a signature of smith or some inscription, and the surface is not polished to keep them. The reverse is flat and polished.
Obverse
Reverse
