JDM von Weinberg , Feb 26, 2012; 04:30 p.m.
Kadlubeks Objektiv-Katalog shows an SR Rokkor QF 250mm f/4 lens (MNT0480) from 1958-62 "with EV indicator". Earlier rangefinder lenses were marked in cm, but nothing so long as 25cm is listed.
The price of the one above that Kadlubek does list is quite high (year 2000, ca. $300), but it isn't likely to be yours. A picture would be really helpful, especially one or more that show the lens markings.