Key: Hi-Mound BK-100
Serial: None
Vintage: Unknown
Acquired: April 14, 2026
Plate: None
Base: Bakelite surrounding Steel
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Review
The BK-100 is perhaps the most common Japanese semi-automatic key in existence. This key was manufactured by the Hi-Mound Electro Company. The company was founded by Takaitsu Takatsuka in the 1950s where it was associated with the Dentsu-Seiki Company and has offered a wide range of reliable, budget-friendly keys over the course of its history. The BK-100 key was introduced around 1953.
To meet the production amateur radio equipment demands of the West during the 1960s, the key building operations at Dentsu-Seiki shifted under the brand name Hi-Mound. The name “Hi-Mound” comes directly from the founder’s surname “Takatsuka”. “Taka” translates to high or tall and “Tsuka” translates to mound or hill.
Hi-Mound operated as the original equipment manufacturer for the BK-100 key design. Importers in other countries then rebadged the key and sold it within their own markets. Some brand names you’ll see are Skillman, Lafayette Radio, Radioshack, Swallow, Eagle, Electro, Calrad, Midland, and many others. In most cases, retailer distributors would not only rebrand the key, but also assign it a unique model number, such as 99-2552 (Lafayette), T.K. 12 (Calrad), or KY-102 (Monarch).
Out of all of the different brand names that sold this key, I’ve only ever seen evidence of a few minor variations of it. The most common, perhaps, is like the one I own and have shown in the gallery accompanying this article. Others look identical to mine, except the speed plate has a black background instead of cream/white. At least one example I’ve seen has an I-shaped damper assembly instead of the T-shaped damper like mine. Almost all examples of this key include only the word “JAPAN” on the underside of the Bakelite base (surrounding a hefty steel base). I say almost, because NØUF shows on his website, a Hi-Mound branded BK-100 that includes both “Hi-MOUND” and “BK-100” cast into the bottom as well as the typical “JAPAN” text. His example includes the I-shaped damper assembly. The only other variation I’ve seen has been with the suction cup feet, where some are black and opaque and others are a clear (or close approximation) semi-soft plastic/silicone material.
Based on some research, some of the earlier BK-100s from the 1950s into the early 1960s have bases with orange undersides and the speed gauge are cream/gold. From the mid-1960s onward, you’ll find the undersides of the bases to be painted gray and the speed gauges will be black/chrome. That same research suggests the timing of the base color change coincided with the changeover of key operations from Dentsu-Seiki Co. to Hi-Mound Electro Co. which happened around the mid-1960s.
The clear plastic cover for this key is difficult to find in good repair. The cover on my key fits extremely snug on the Bakelite base and I image, if this is the way the majority of these keys are, then the cover gets cracked and broken as users put it on and take it off of the key when making adjustments. The cover seems very fragile. Luckily, my key has its cover and it’s in pretty good condition. I use a small plastic wedge to gently pry the cover from the base when I use this key and need to make an adjustment.
The BK-100 is quite noisy and I guess that’s expected in a budget key like this. Placing the cover on the top quiets the key down only slightly. As a person who does not like noisy keys, I’m happy to include this one in my collection, but I never actually use it.
Any serious collector of Morse keys should have a “Coffin bug” amongst their other keys, but since the BK-100 keys were made in such abundance and by so many different brands, they shouldn’t command a high asking price and you should not need to pay very much for one in nice shape with an intact and unblemished dust cover.
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