this must be the death reg you refer to
Kathleen Mary Harris
born 1 Oct 1905
death reg Mar 1973
age 67
Cirencester
7b 1106
the only problem is Kathleen Mary Crewe daughter of Charles and Fanny was not b 1905
This looks like her birth reg
Kathleen Mary crewe
Dec qtr 1903
Cirencester
6a 390
ages onn death certs are only as accurate as the informant knows
So possibly Kathleen had told everyone she was 2 years younger than she really was
a birth date of 1 Oct would be reg in Dec qtr
so maybe "your" Kathleen was born 1 Oct 1903 not 1905
You really need birth cert to confirm
You state you already have birth cert and marriage cert
Could you post details from those certificates?

Suz