Technical: SUGATA - HEIAN KOSHIZORI where the arc straightens in
                    the upper. KO-KISSAKI. Origins are  
                    YAMASHIRO style, some early pieces may be in
                    that style. Shallow height of the back ridge.
             HADA - Finely worked MOKUME or ITAME/MOKUME mix with
                    a cast of deep transparent blue. CHIKEI and 
                    JI-NIE. NIE JI-BA may be found. KO-BIZEN is
                    known for very healthy steel, a noted point.
            HAMON - Finely done KO-NIE in NIOI-FUKASHI KO-MIDARE,
                    SUGU KO-CHOJI. Perhaps wider MIDARE BA of 
                    GUNOME and CHOJI mixes defined of ASHI, 
                    KINSUJI and SUNAGASHI. Some lines undulate in
                    height, and there will be a high degree of 
                    complexity.  
            BOSHI - SUGU or SUGU KO-MIDARE with KO-MARU.
           NAKAGO - Long, gently curved HEIAN styles. 
                    Some were KIJIMATA. Signatures are usually
                    the smith name only, but some longer.

There were two original KO-BIZEN groups: TOMONARI followed by 
MASATSUNE. Traditional study teaches KO-BIZEN began in EI-EN 987 
with these and other smiths. Present examples appear from NIN-PYO
1151, and are the subject of most modern descriptions. The early 
dates occupy a hallowed throne in scholarship and need not be 
violated, as appraisal should always fall to correct placement 
of time for individual pieces. GEN-RYAKU smiths are said to be in
the 5th generation.

The order of importance in appraisal consideration for KO-BIZEN:

     1st - TOMONARI

     2nd - MASATSUNE

     3rd - NOBUFUSA and his "Three HIRAs"

Appraisal: HEIAN BIZEN swords will bring TOMONARI and MASATSUNE 
           to mind. The first step is to weigh a differentiation 
           between these masters. 

           TOMONARI  - Look for O-HADA.  
                     - Narrow YAKIBA in BOSHI has small KO-MARU
                       or TOGARI-like head.
                     - NAKAGO is refined. Flattened KURIJIRI is 
                       HA-AGARI (HA raised) or even slightly 
                       KATAYAMA.
           MASATSUNE - Tight, well-knit grain. 
                     - CHU-SUGUHA BOSHI with KO-MARU and short
                       KAERI. 
                     - Original NAKAGO seems comparatively crude
                       and terminates in rounded KURIJIRI.

Note: -KO-BIZEN mark is very healthy steel. One doubts one's eyes.
      -Long, bold signatures: Look to TOMONARI School.