This Mitsubishi 6X-870 is a favorite of mine. I just picked this one up (with it's leather case) on Ebay. it had just been listed with a Buy It Now of $9.99. It was very dirty and was missing some paint on the speaker grill. As you can see I have cleaned/polished the case and touched up the missing paint. Works well.
I am uncertain of the manufacturer of this great looking radio. I know that Shirasuna Denki Mfg. Co. Ltd of Japan (Silver) made several Mitsubishi radios, perhaps they made this one too. Although Mitsubishi was (and still is) a major industrial juggernaut in Japan they did not make their own pocket radios.
This radio appears on the front cover of: "Collector's Guide to Transistor Radios"
2nd edition by Marty & Sue Bunis (1996)