Nice thing about FTR is that the ones released relatively recently will have a much better chance of being in super-good condition, simply because they were FTR'd more recently. If you're looking at a World War I rifle with FTR stamps, the thing could have been FTR'd in 1917 and then used roughly ever since.
If you are looking at an FTR, thing to do is to check the FTR date (stamped or engraved on a Number 4) and, on ANY SMLE, check the barrel date. Barrel dates on SMLEs are the date of the installation of the new barrel and are the equivalent of the FTR stamp on the later rifle. There was one here the other day, in this forum, a 1917 Enfield that had a '23 barrel date. Obviously, the rifle was completely rebuilt to 'as-new' in 1923, so it only has ONE war's wear-and-tear on it since rebuild.
It can get confusing, but at least the British Empire marked its rifles. A lot of places didn't.
Ivan, for example, simply had a barrel date that was part of the factory information. This is why you can get a Moisin-Nagant with an octagonal receiver, the Tsar's signet and a 1938 date, even though the octagonal receiver was old history by that time and the Tsar had been dead for 20 years. What you are looking at is the BARREL date. If it's Izhevsk, it might actually be a Remington or a Westinghouse or a Sestroryetski or Tul'ski receiver.... but the 1938 IZHEVSK barrel information misidentifies the entire specimen...... although it does tell you indirectly that the rifle was REbuilt in 1938, at Izhevsk. VERY confusing.
British practice was much easier to keep track of.
Have fun!