Again, really terrific work Kris!!! You are a gem!
I will certainly be ordering a printout of this entry from the CRO.
I saw this in the IGI and the name 'Walter' just didn't sit right with me. I don't want to sound obsessed with the patronymic/matronymic naming thing, but there are no Walters among Thomas and Mary's children. They are:
JOHN MICHELL: Christening: 23 AUG 1807 Cubert, Cornwall, England
ELIZABETH MICHELL: Christening: 05 NOV 1809 Cubert, Cornwall, England
SIMON MITCHELL: Christening: 02 MAY 1813 Cubert, Cornwall, England
MARY MICHELL: Christening: 21 APR 1816 Cubert, Cornwall, England
MARTIN MITCHELL: Christening: 10 MAY 1820 Cubert, Cornwall, England
So although Thomas and Mary had three shots at christening a boy 'Walter' after the mother's father, they didn't take the opportunity. (Not that it always follows that the father gets honoured through the names of their grandchildren - my William Mitchell had 5 sons and not one of them was christened 'John' after his father ... mind you, William was married very young to his 7 months pregnant girl at the St Columb Register Office instead of at church, maybe not reflecting so well on a father who was a Wesleyan Lay Preacher, perhaps there might have been just a bit of a falling out there ... ).
So anyhow, Thomas and Mary didn't use 'Walter' but they did use 'Martin', and he was christened as such on the day his mother was laid to rest. Also, the name 'Martin' never appears to have been used before in this Mitchell line, so there should be some compelling reason to use it above other choices. (Mind you, I'm not sure about 'Simon' either, but that's another story - and I haven't dug back into the Pearce/Adams families much yet of course!)
When I read the transcription of 'Walter' in the IGI I checked the Cornwall Parish Database and, like you Kris, found Walter and Elizabeth marrying in Roche in 1763. It's not out of the realm of possibility that we are talking about a Cubert christening record for one of their children. However it does seem a remote possibility, especially given elapsed time from marriage to christening, some distance between parishes and the seeming lack of evidence that Walter existed otherwise in Cubert. Contrasting with that, there is a Martin Pearce in Cubert - marrying Elizabeth Lawer on St Valentine's Day 1767. Thomas and Mary's first daughter is christened 'Elizabeth'. Also, although it doesn't look like it in type, it's not impossible for someone transcribing a damaged old register in copperplate writing to confuse 'Walter' for 'Marten' or 'Martin'. You've demonstrated how confusing and subjective the interpretation can be most ably in your last response - even worse when you're dealing with the limitations of the microfiche reader!
I guess these things explain why I had the hunch about 'Martin' and why I agree that getting the printout might help. Although now that, like you, I'm a bit convinced about 'Walter' being 'Martin', I'll need to show it to some independent third parties to get an objective interpretation!
Kindest regards
Grant Limeburner Mitchell