LT77 box with two serial numbers

I currently have my lt77 out of the landy to clean it up and check it over before the engine goes in and iv noticed it has two serial numbers the 11 digit landy one and a 4 digit one underneath (all numbers)

Ive looked online and i can only find an ashcroft rebuild number which has 6 digits inlcuding one letter

Anyone got any ideas as to if its a rebuild number or not ,if so where it was rebuilt ? its an early suffix E box and id like to know if it was maybe modified with parts from a newer style suffix G or H box

Thanks

Numbers are 31a0276578e and 5180 being an E i think its too early to be a tdi box