What’s more enticing to collectors than a gorgeous example of one of the most beloved Ferraris of all time? How about the initial prototype that helped shape that model?

RM Sotheby’s will auction off the first 365 GTB/4 prototype later this month. Not only is the car up for bid the first Daytona, but it’s also one of the most unique, with a host of features that didn’t make it to production.

The pressure was on Ferrari in 1967. The year before, Lamborghini had launched the Miura, the first supercar with a mid-engine design. Rather than following the Raging Bull’s lead at that moment, the Prancing Horse decided to build one last sports car on its long-running front-engined V-12 platform. That model would be the beloved 365 GTB/4, or, as it’s best known today, the Daytona. That nickname, which came from the marque’s 1-2-3 finish at that year’s 24 Hours of Daytona, is unofficial, but it’s stuck for more than five decades now.

You can very clearly see the car the 365 GTB/4 would become in the first prototype, but there are also a number of key differences. Many of them will jump out immediately to anyone who’s spent enough time admiring the coupe’s stunning Pininfarina design. Chassis no. 10287 has a much more traditional front fascia with round headlights and a less prominent grille, while the back features smaller taillights, a shorter trunk lid, and a single-piece bumper. The silver two-door is still a beauty, but the details do change the car’s look ever so slightly.

The biggest difference between the first Daytona prototype and the finished version can be found under the hood, though. This example is the only 365 GTB/4 powered by a 4.4-liter Tipo 243 V-12 with six Weber carburetors. It’s based on the mill found in the 330 GT and comes equipped with a dry oil sump, dual ignition, three valves per cylinder instead of four, and twin sparkplugs per cylinder.

The prototype was completed in early 1967, despite being titled as a 1969 vehicle. It was used extensively for testing and then sold by Ferrari in May 1968 before the production version even made its debut. It has passed through the hands of a number of collectors in the decades since, though its current owner’s family has possessed it for nearly 20 years, according to the listing. The road-going car, which retains its original chassis and engine, was fully restored early last decade and is Ferrari Classiche certified. It’s in such good shape that the car was actually displayed at the Museo Ferrari from 2015 to 2016.

The first 365 GTB/4 will be sold in a single-lot auction that runs from Monday, May 22, to Friday, May 26. No estimate has been announced, but the second Daytona prototype sold for US$2.3 million (HK$18.4 million) last August. It’s not hard to imagine this car selling for even more.

Click here for more photos of the first Ferrari 365 GTB/4 prototype.