In regards to the attribution, the NBTHK will, when they think an item is almost a work by someone, as they believe in this case, will use the word Den. It means it has most of the qualities or elements that make a work by Joushin, it may be missing some features, or it may have more than is normal for him, it may be his very best work and it looks different for this reason. It is for these reasons the NBTHK will opt for the Den attribution. It is by no means a bad thing and should not be thought of as lesser in quality.
The theme is described as Yadougu no Zugara 矢道具図柄 and shows the tools required for archery. These include Yabane 矢羽 (arrow-feather), Yazutsu 矢筒 (arrow-tube or quiver) and other items. Finished in takabori kin utori iroe (高彫金うっとり色絵). The shakudô is a rich black in colour and the nanako is fine and even in the style of the early Goto masters. The condition is excellent. As Jôshin has no students I can find, and was very fond of making other items for the samurai including battle equipment, it is possible this Kôgai is made by Joushin, it seems to suit.
In regards to the Warabite 蕨手, this is also reminiscent of Joushin. In his book Ko Kogai, Ikeda shows how there is a difference between the work styles of Yujô, Sôjô, Jôshin and the other Gotô artists. There is a section there that looks at the Warabite of Ko Gotô, Ko Kinko and Ko Mino kôgai. In the section relating to Joushin, all examples have Warabite with the same trait as this sample. The section of the warabite, half way through both side sections that leads up into a point is much taller and sharper on examples by Joushin than the other artists (see the image below where the arrow is pointing).
This feature, along with the fuller design points to this being a work by Joushin more so than other Goutou artists around his time. Looking through the books like Ko Kôgai, Gotô-ke Jushichi-dai and Toso Kodôgu Koza, I see this to be a consistent kantei point and something to be studied in the years to come.
Jôshin was born in 1505 and died on March the 6th, 1562. He was the eldest son of Gotô Sôjô and was a samurai retainer of Ashikaga Yoshiharu and Ashikaga Yoshiteru. On April 5, 1528 a riot broke out in a camp enclosure where Joushin was stationed. He battled the insurgents and drove them off. In temperament he was very strong, brave and courageous and these traits can be seen in his work. His work is bold and vigorous and he shows a great strength of depth in his carving. He also designed battle equipment, armour and other military items. This influence can be seen directly in the design of this kogai. In 1562, near a lake in Ko Sukemoto he fought in a battle, and before dying, gave his jusu (数珠 beads or rosary) and sword to be taken to his wife. His wife was the daughter of the famous painter Kanou Masanobu 狩野正信. She was known as Myoushin.
Size, Total length 228mm x Dô width 13.2mm and Sao width 6mm.
The Origami translates as follows.
矢道具図柄, Yadougu no Zugara (Archery tools motif Kogai)
無銘, 伝乗真 Mumei, Den Jôshin (unsigned, in the style of Jôshin)
赤銅 魚子地 Shakudô nanakô-ji, 高彫 Takabori, 金うっとり色絵 Kin uttori iroe, 蕨手金象嵌 Warabite Kin Zôgan (Shakudo nanako (fish roe) surface, High carved, Gold wrapped finish with a worn look, the Warabite is inlayed in gold)
Migi wa tokyokai ni oite shinsa no kekka hozon tosogu kanteshi kore wo shosuru (Examination by the Tokyo branch has resulted in the decision that the item to the right is a sword fitting that is worthy of preservation)
Heisei Ni Ju Nen Go Gatsu Ni Nichi (May 2, 2008)
Zaidan Hojin Nihon Bijutsu Token Hozon Kyokai (Incorporated foundation Nihon Bijutsu Token Hozon Kyokai)