the first ones without flutes were the 50th group, in 1983. I seem to recall that the flat SR cranks were released in 1987, but I could not verify that with a short check on the web. 11 is the date code for "no date code".

after 11 the date codes really get weird, as is the case in a lot of bar scenes, too.

there was one more version after this one with a lasered logo.