That's because 266V is not actually a valid voltage for anything. Eurodrive, being a European company, makes motors for countries OTHER than the US. Those motors can be used here though. it's kind of a long story if you want to TRULY understand, let me explain by building a case (or just skip to the end):
1) Here in North America we use 60Hz power. Almost everywhere else in the world, they use 50Hz power. Without getting into the whys and wherefores, suffice to say it's just because AC power was developed separately and almost simultaneously on opposite sides of the Atlantic during an age when long distance communication took months, not nanoseconds...
2) Our voltage standards are different here compared to "over there": Us; low voltage distribution is 600V, 480V, 240V, 208V 3 phase and 277V, 240V or 120V single phase, depending on where you are and what you are doing. Them; a relatively new "harmonized" system of 400V (or 230V*) 3 phase and 230V single phase, but really depending on the actual country, the "400V" is going to be 380V, 400V or 415V with a corresponding single phase voltage of 220V, 230V and 240V respectively.
3) In the 3 phase Wye (Star) systems, the RELATIONSHIP between phase-to-phase voltage and phase-to-neutral voltage is the square root of 3 (1.732). Hence, on a 480V wye system, we call it 480Y277 meaning 480V ph-ph and 277V ph-n. Over there, it is 400V ph-ph and 230V ph-n.
4) Over here, we have a SEPARATE system of standardized voltage levels called "Utilization Voltage", for things that USE electricity, as opposed to what it is DISTRIBUTED as by the utilities, because our distances are longer, so we EXPECT that there will be "voltage drop" between the service entrance and the location of the machine, i.e. the motor. The corresponding Utilization Voltage then for 480V is 460V (240V = 230V, 120V = 115V, etc., you get the picture). These are enshrined in a set of standards from a non-profit organization called "NEMA", the National Electrical Manufacturers Assoc., using a standard called NEMA MG-1 (MG = Motors and Generators). Those same standards were then adopted by the semi-Governmental agency called the American National Standards Institute (ANSI).
5) A similar system, called "IEC" (International Electrotechnical Commission) exists in the EU, but not so on the different votlage standards, at least not in the same way. 400V means 400V there, whether talking about distribution or utilization. But remember, that is ALREADY a "harmonized" level, a compromise, because of all the different countries having different actual voltages. Besides, things are so crowded there that voltage drop between service and load is minimal as well because they are on top of each other.
6) Motors convert electrical energy into mechanical rotating energy, measured in torque and speed. The shorthand unit of measure for both together is what we call "HP", over there they call it "kW", meaning MECHANICAL kilowatts (we use kW only for electrical values). But the chief thing we USE motors for is torque. Speed is consequential to the number of motor poles (coils) and the frequency.
7) Motor design Torque, meaning what we EXPECT from it, is dependent upon the RATIO of the voltage AND frequency together, because that is what creates the magnetic flux that makes the motor spin. That V/Hz ratio then is what we must judge a motor design's performance against. Here, and there, the design criteria is that a motor will produce the DESIGNED torque at the RATED voltage and frequency ratio, +-10%. So here, 460/60 = a V/Hz ratio of 7.67:1. Over there, a 380V 50Hz motor (the original pre-harmonized predominant design) is 380/50 = ... a V/Hz ratio of 7.6:1! Almost exactly the same, and not by coincidence. 400/50 = 8:1, still within the +10% rule. That means you can safely use a 400V 50Hz IEC motor over here as a 460V motor, and you can safely use a 460V 60Hz NEMA designed motor over there at 400V 50Hz.
8) As noted in #2 above (*), a FEW countries and areas, predominantly those influenced bu the UK, use 230V 3 phase in some areas. Because of that, most IEC motor mfrs make "dual voltage" motors by using 6 leads that can be configured internally in a Delta pattern for the low (230V) supply, and a Star (Wye) pattern for the High (400V) supply.
9) Over here we have dual voltage motors as well, but for us they are simply two sets of identical winding inside of the motor, and we connect them in SERIES for 460V and in PARALLEL for 230V, because for US, the two different voltages are 2:1, not 1.732:1.
10) Finally... So when an IEC motor manufacturer, such as Eurotherm, sends a motor over here that was DESIGNED for 400V 50Hz to be used as 460V 60Hz, the second (low) winding connection will NOT be suitable for 230V 60Hz, because the V/Hz ratio will be incorrect; 230/60 = 3.83:2, 230/50 = 4.6:1, and that is MORE than the +10% allowance (17% actually). So to help AVOID having someone over here ASSume that they can use that motor at 230V and burn it up, they LABEL it as 266V, because that's what it is; 460/1.732 = 266!
