often had their own design bureaus). This consisted of between one and three letters and the project number. For the 122 mm howitzer M1938 mentioned above, the developer index was M-30. Letters identified the developer or producer. For example, M stands for Motovilikha plant No. 172, A - for KhPZ No. 183, B – for ‘Bolshevik’ plant, S – for Central Artillery Design Bureau, D – for Factory No. 9 and so on. There were two exceptions: ‘Arsenal’ plant No. 7 (they used a '7' digit instead of a letter) and the artillery plant No. 8 named after Mikhail Kalinin (their project number was placed first, followed by the 'K' letter). Examples of these designations include 7-2 and 61-K or 20K (variants with and without a dash are both widely used in historical documents). During the World War II some indices changed: Plant No.7 was named after Mikhail Frunze circa 1940 and changed index to 'ZIF'; Plant No. 8 after evacuation to Sverdlovsk used 'KS' index placed before the project number; Plant No. 92 got index 'ZIS' after renaming to Zavod imeni Stalina in December 1940 or January 1941. The artillery sharashka OTB of NKVD (in 1938—1941 and 1944—1953 it was located in Kresty Prison complex in Leningrad, in evacuation it was housed in the buildings of Plant No. 172 and named OKB-172) had no special index, but often used 'BL' letters after Lavrentiy Beria. For some pieces of artillery, both the Army and developer names were well known and interchangeable, such as the 76 mm divisional gun M1942 known also as ZIS-3. For some other guns, such as the 45 mm anti-tank gun M1937, the developer index (53-K) was very rarely used, even in literature of the time. Further modifications - 1950s This system was used throughout and well after the Second World War. In the 1950s, another change took place. The year was dropped from the official names of newly designed pieces, and instead of the M19XX (обр. 19ХХ г.), the developer index became used as the unique identifier, e.g., 122-мм гаубица Д-30 (122 mm howitzer D-30). The change was not applied to old pieces, e.g., the D-1 was still referenced as a 152 mm howitzer M1943, and not as a 152 mm howitzer D-1. The third change was connected with introduction of the GRAU system of indices for ordnance, weapons, and munitions. After this introduction, the developer