The Guild S-300 came in a number of variations, the model pictured is an S300-AD, signifying (A) ash body and maple neck, and (D) DiMarzio PAF and Super Distortion humbuckers.

Guild S-300 - New Generation of Solid Bodies By Guild
United Kingdom Guild advertisement for two new solid body models, the S-300 guitar and single pickup B-301 bass.
Guild S-300 - The New Guilds Are Here
Late 1977 UK advertisement for the new Guild S-300 guitar and B-301 / B-302 basses. The S-300 (in white) is advertised as available with Guild (as shown) or DiMarzio pickups. The bass pictured is t...
Guild S-300 - Youve made it the most popular solid body guitar weve ever built
The Guild S-300 came in a number of variations, the model pictured is an S-300D, signifying the standard mahogany body and neck with (D) DiMarzio PAF and Super Distortion humbuckers. Non-D versions...
Guild S-300 - Balance of Power
1981 Guitar Player advertisement for Guild solid body guitars, featuring the S-300, available since 1977. The S-300 was available with different body and neck woods and a choice of Guild or Dimarzi...