Thanks for the detail shots David.

It's interesting needing spacers/risers... I mean, they worked it into the design effectively but it begs the question of why did they need spacers/risers? I think all stems from the neck sitting so high in the neck pocket right? What if the neck was lower, like a Fender - no need for bridge/pu spacers/risers. Is it possible JB was thinking about an upright bass where the string are far away from the body? I can't imagine it being a club-footed engineering/design issue, especially because Fender already set a successful standard for such.
My '63 Burns of London Vista Sonic has small knurled cap machine screws into insets. I got them (vintage NOS) from a source in the UK through the Burns fb page. The bridge base is the opposite of the Meazzi - it's sunk into the body!
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One of the saddles was missing when I got it so I made one of brass for it - 4 holes above the bridge are for a mute. (missing) I'd like to find one someday. Someone added a mini-toggle kill-switch, which is a decent mod - otherwise it's mostly original. Pat Wilkins did the awesome, slightly translucent red finish based on one of Jim Burns' finishes. It's all about little details.
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Bridge cover is new but exactly like a vintage one - again, got it from the same UK source.
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