Late 1970s and early 1980s Guild BT-4 combined bridge / tailpiece for bass guitar. This bridge was first fitted to the final examples of the Guild JS and the new B-301 basses in late 1976. Also the stock bridge for the B-302, B-401, B-402, X-701 and X-702, SB-201, SB-202, SB-203 and SB502E basses.
Part number 90526. Described as follows in the 1978 Guild catalog:
new solid brass bridge/tailpiece that gives you perfect intonation
The BT-4 was not as adjustable as some modern bridge designs but was a significant improvement on previous Guild bass bridges. saddles are adjustable from side to side, back and forth but not independently up and down. John Entwistle was not a fan, singling it out for criticism in his review of the B-301 bass for UK magazine Beat Instrumental.
One significant downside to this bridge is the short distance between string end and saddle, which can result in the silk wrap of some bass strings extending as far as the saddle, as seen below. Unwrapped strings are available, for example La Bella.
List of Guild bridges and tailpieces

A Guild BT-4 bridge/tailpiece fitted to a 1977 Guild B-301 bass.

The BT-4 bridge/tailpiece is mounted with two slotted bolts. A third smaller screw prevents tilting.

Guild BT-4 bass bridge/tailpiece - baseplate and saddle detail. The saddles are threaded onto perpendicular bolts - allowing lateral adjustment for perfect string spacing.

Guild BT-4 bass bridge/tailpiece, rear view. The strings enter through the back of the tailpiece.

This bridge seems to have a wide range of adjustability, with such long screws - however the short distance between saddle and tailpiece mounting necessitates the use of silk-free strings



Underside view

mounting bolts

The bridge sockets, and metal support for the tilt-prevention screw
$600
$80
$120
$219