This an exceedingly rare card of Sadaharu Oh. The JRM 39a set carries an R5 designation in the Japanese Baseball Card Checklist & Price Guide, Vintage Edition 2.1 by Gary Engel, meaning that five or fewer copies of this card are known. JRM 39a cards are slightly larger than JRM 39b cards. There are five different cards of Sadaharu Oh in the JRM 39a set. This card is described in Engel's Guide as "Sadaharu Oh blue background with bat". The text printed at the top of the card back is "Giants Furikake". This card was most likely a promotion for a product from the mid 1960s. Furikake is a condiment meant to be sprinkled on top of rice.
Size: 1 3/16" in diameter.