A J50 or J45 I think??

I have recently swopped a new shinny Takamine EAN 45C for a beaten up Gibson acoustic with a tone to die for - Love at first strum.

I think it is a square shoulder J50 from the 70s but here is a brief desciption for anybody who can help.

The Gibson logo is plain gold and the "i" joins the top of the "G"
The serial is - 623599 (in black ink).
It has MADE IN U.S.A. stamped into the wood under the serial number. Under the S in U.S.A. there is "2" stamped into the wood.
It has a unbound rosewood finger board -20fret joined at the 14th.

The Body has black binding top and bottom with thin gold/black/gold stripe , square shouldered and looks to be solid top and sides.
There are 3 rings around the sound hole - the outer has one gold/black/gold stripe. The middle has 3 and the inner has one.
There is a rosewood non-adjustable bridge which has a slight belly down to the tail of the guitar.
The pick guard is a black tear drop shape.
The tunners have been changed.

Thanks Ian from Liverpool