Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_60 ( quantity INTEGER, year VARCHAR, model VARCHAR )

### Question ###
Name the sum of quantity for before 2011 model slf-230

### Accurate SQL ###

SELECT SUM(quantity) FROM table_name_60 WHERE year < 2011 AND model = "slf-230"