Standard windup key for most tin toys. Each key may appear a little different. Some are solid and some have circle punch holes. Tip of key is approximately 1/8" square shape measured on standard ruler. Same size as most keys from the 50's through present.  There are a few exceptions for German toys (Marx, etc.), and toys produced before 1950.  Not sure about the Russian Toys. Please be sure to read this description since not all keys are the same. If you need the key to be wider you can open it more by using needle nose plyers, inserting and opening more, or straight edge screwdriver inserted and bend in slot.