[2] The first trial boat, numbered 18-02 by the RNLI, was built by W. A. Souter of Cowes.

The helm was in a standing position, in a sunken bridge deck, with a weathershield in front of the controls.

[3] in September 1969, following successful trials, the RNLI placed an order for 4 boats with boat-builder William Osbourne of Littlehampton, to be constructed with GRP hulls, fitted with twin sterndrive Ford 60 hp marinised petrol engines, and each costing £3,400.

[3][4][5] In the early 1970s, it was decided to reclassify the 17 and 18-foot boats as A-class lifeboats, and their numbers were changed according; 18-004 becoming A-504, 18-007 becoming A-507 etc.

[6] A-504 (formerly 18-004) at Weston-super-Mare, was launched at 10:30pm on the 13 September 1975 into an easterly gale, to a motor-boat stranded on the rocks.