In Japan these cancellations are called "hanagata iri Yokohama in" (Nishino-Tani) and they were used between 1878 and 1884. They are in black and have a diameter of 21 mm.
 

4y2: Cover with 10 Sen old Koban (9s perforation) fromHiogo via Yokohama to Germany. Hiogo HG79A white cross obliterator Hiogo Early Large Single Circle Type C3: 23 JAN Yokohama Experimental type with asterisk and year (Y2): JAN 28 1879 NEW YORK BRITISH TRANSIT SCHIPPENBEIL arrival mark: 12 3 97  Jan 28 1879 is the only date recorded for this type Y2 cancellation. Mr. Swenson has records of only 2 of these strikes (neither is mine according to his description), but both of them have  the same date as mine. Was this postmark really in use for just one single day? The City of Tokio of the Pacific Mail Steamship Co. was leaving Yokohama on the 29th, which would explain the markings on the 28th. But which Yokohama marking was used for the sailing before and after?

 

4y3: 2 Sen old Koban, olive, 1876 issue.  Yokohama Experimental type with star and month, date, year sequence (Y3): Oct 11 1879  Remarks: This type of date stamp was seldom used to cancel a stamp as shown here. Obliterators were used for that purpose as shown below.

 

4y4: Foreign Mail Postcard 3 Sen, 1879 issue, FC5, from Yokohama to Dresden and forwarded to Leipzig, Germany.  Yokohama Large Flower killer, Amano type 326.  Yokohama Experimental type with star and month, date, year sequence: Nov 26 1880, type Y3 Dresden Arrival mark 1881. 01. 07  Delivery mark: January 8.  Remark: another example follows with a different kind of obliterator.

 

4y5: Foreign Mail Postcard 5 Sen, FC2  From Yokohama to Friedeberg, Germany  Yokohama obliterator, probalby a damaged YH79B type. Yokohama Experimental type with star and month, date, year sequence: SEP 21 1879. Type Y3 This is a late usage of the FC2 5 Sen postcard. The 5 Sen postage for postcards to UPU nations via the USA was reduced to only 3 Sen on April 1, 1979.

 

4y6: Cover with a 5 Sen UPU Koban from Tokyo via Yokohama and San Francisco to Amhurst, Mass. Tokyo Flower daub obliterator in black Tokio Small Single Circle: 19 JAN 1884 Yokohama Experimental Type with star and day/month/year sequence: 20 JAN 1884 (Y4) San Francisco PAID ALL: Feb 15 (on back)

 

4y7: Foreign Mail Postcard 3 Sen, 1879 issue, FC5  From Shanghai via Yokohama and New York to Wilhelmshaven, Germany.  Killer unclear - a damaged crossroads killer? Small Single Circle Shanghai, 20 Nov 1884  Yokohama Experimental type with old postoffice emblem: 29 NOV 1884 (Y5) New York transit Dec 27