There are many methods of restoring your original design.
Sympathetic Restorations entail a careful "interpretation" of the original architect's style and design intent and then retrofitting such to the modern context of maintenance and play. Length is typically the additional ingredient. For instance, this would require not only recapturing lost carry bunkers, but also moving them further away from the extended tee to account for today's issues of length. Here, architects endeavor to take the course "back to the future". A sound understanding of the architects' philosophies and a reasonable interpretation of his design intent compliments such an adaptation. Timuquana is a good example.
Pure Restoration would require returning a course and its features back to its original sizes, shapes, positions, and distances exactly. However, massive amounts of historical evidence must first be acquired. (aerial photographs, topographical images, routing plans, green sketches etc.) Plus, original green sizes and can be determined through core-lines, and bunker shapes and depths can be determined through excavation....peeling back the accumulated excess. Pure restorations seem over the top in the modern context though. A 5,800 yard course is a museum piece for play. As Crenshaw once said, scalping your entire premises of all trees would be unreasonable..... though Oakmont has done an excellent job persuading us otherwise.
Date Specific Restorations: Merion
Comprehensive Restoration embodies the revival of the classical elements. Here, emphasis is diverted from the complex measurements of sizes, shapes, positions, and distances of the original features. Instead, the focus is placed on the common facets and characteristics inherent in the classical game. This includes recapturing variety and strategic choices through open spaces; reviving the mental elements of thought, mystery, decision making, shotmaking and recovery play; restoring firm, fast conditions in the fairway and through the green; and reinstituting complimentary turf conditions with a variety of natural textures and contrasts.
Most of us freely toss around this buzz word, "restoration", without qualifying its specific type: 1. "TRUE/PURE" 2. "PARTIAL/DATE-SPECIFIC" 3."SYMPATHETIC/EMPATHETIC" 4. "COMPREHENSIVE". Such terminology becomes more confusing when "renovation" is thrown in the mix. There's a difference.