It would be an "N" frame (large frame) made in 1970 (model 27 or 28).Ok, N61575 would be a frame made around 1970
When would a K61575 and L61575 frame be made ?
There are no K frame (medium frame) 357's made with K61575. There is no L prefix serial numbers.
And trying to figure out what gun you had with what is either an assembly number or incomplete serial number is futile at best.
Jim