Which pickup was my Rickenbacker 4001 born with?

I'm the owner of a 1969 Rick 4001 (serial# IE410 corresponding to May 1969). The bridge pu has later been replaced with a J-bass style one and I'd like to restore the bass to original condition. I read that Rickenbacker discontinued the horseshoe pickup and introduced the Hi Gain pickup in the same year. Anyone can tell which bridge pickup my Rick was born with? I can buy a 1975 Hi Gain bridge pickup, would it fit on the bass?

 

Yes, everything else but the pickup is original