I've not heard of a baptism certificate. When and where did such things exist? 
Hi Mark,
I have Baptism, Confirmatiom, & Communion Certificates back to my Gt-Gt grandma in the 1840s, one for my Grandad Born in 1904 - Grandad has a wonderful Certificate listing his birth date, his Baptism date, the date he was "Presented" to the church, his Confirmation date, Communion Date, and Marriage date (Gold dust for me!) .................
I also have my own from the 1960's, my sister & Brothers from the 1970's & 1980s and my nephew has one from last year.............
(Luckily for me my family are all born hoarders and dont throw much 'official' stuff away!)
They both CofE & Methodist church ones, I think its down to the individual churches to supply them and the parents to keep them updated after that.
Gaille