Hardware Design
Here's details about some
parts in the Kent 820.

The Kent 820 Bridge
The original Kent 820 Bridge is an excellent design; Used in both 6 and 12 string 820,
each string Saddle has many 'notches' which allow for string-spacing in approximately
1/32nd steps, and the long adjusting screws allow for an excellent range of front-to-back
'travel' for fine-tuning and setup, a lot more travel than a Gibson Tune-a-Matic bridge.
Up and down adjustment of bridge-height is done through the two 
threaded posts which are also the Bridge Mounting Posts.
Curiously, a Gibson Tune-a-Matic bridge fits perfectly on the
Kent 820 mounting posts, no alterations required.
I think Gibson copied this Kent bridge design and used it in their 1970's and 1980's
solid-body guitars calling it
The Nashville Bridge.

The Kent bridge also came fitted with a Mute attachment which can be set or disabled with
the palm
of the hand as one plays, but they are not very effective at muting the strings.
After many tries, I discovered that shaping and attaching a piece of thick Piano Felt
over the black rubber underlayment shown in the picture, works great for a String Mute.
The Felt needs to be carved so that it forms an 'Arch' at the center.
Note that the palm mechanism is found on either the left or right side of the Bridge.

The following short audio clip shows a muted electric guitar sound.
Vibrato Springs
I have found different-Tension aluminum springs in Kent 820 whammy bars, (Vibratos).
As you can see in the picture, the two springs are the same Height, but each has
a different amount of turns. The one on the left side has less turns but is about 25% harder
than the one on the right, which has more turns. 
Both springs are ineffective in my experience, they need to be much harder to bring
the strings back to Pitch. Kent made their own Vibratos and their only weakness are the Springs, otherwise the Kent Vibrato parts were precision-machined, polished stainless steel parts.
Notice the two identical Kent Ads below:
The ad on the left shows the 820 with a Bigsby vibrato,
The ad on the right shows the 820 with the Kent vibrato.
Standard Tailpiece fitted to the Kent 820-12-string
and to some 6-string models made without Vibratos
Kent 820 with the Bigsby-style Vibrato notice it does not say 'Bigsby'
Kent 820 with the Kent-designed Vibrato
a totally original Kent 820 6-string model will look like this:
© JAMR 2019