Hallmarks run from Jan 1st and are changed to the next letter on the following Jan 1st.
Sleepy was correct in saying 1934, the letter K would have been in use from the 1st Jan 1934 through to 1st Jan 1935.
As these medals were to commerate the silver jubilee in 1935 they would have had to have been assayed in 1934 to carry that mark.