I recently received an Altaya 1:72 Su-35 model. This model has the #703 written in the nose section right under the cockpit canopy.

There exists a real Su-35 #703 in Russia. I included photos below of the real aircraft and the model I own.

Here is a shot introduction about the Su-35 from wikipedia:

The Sukhoi Su-35 (Russian: Сухой Су-35, NATO reporting name: Flanker-E) is a single-seat, twin-engined supermaneuverable multirole fighter. It is a derivative of the Su-27 'Flanker', and was initially known as the Su-27M. More than a dozen of these were built with some used by the Russian Knights aerobatic demonstration team. The Su-35 had been offered to many countries, including India, Brazil and South Korea.

In the 1980s, Sukhoi was looking to upgrade its high-performance Su-27. The resultant Su-35 embodies aerodynamic refinements to give it more maneuverability, greatly enhanced avionics, longer range, and a more powerful engine. The first prototype, converted from a production Su-27, made its maiden flight in June 1988. The Su-35 was further developed into the Su-37, which has thrust-vectoring capabilities, and the Su-35BM, classified as 4++ generation fighter by its manufacturer. The new model entered into serial production as the Su-35S for the Russian Air Force in 2010.