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Ultimately I’m looking to sell this but I can’t work out exactly what engine it’s from.
The number stamped doesn’t correlate to anything I can find online.

I don’t think the stamped number has any relevance to the identification of the block or the value.

Well it has some relevance it’s 12H and a 1275 engine

Exactly..... 1275cc......, but what configuration is what you want to know........ More pictures might help with an answer

Hippo wrote: ↑Sun Jun 19, 2022 9:53 pm Well it has some relevance it’s 12H and a 1275 engine

You can tell it’s a 1275 from other features, to me the value is the condition of the bore, presence of matching bearing caps etc. The number could have been stamped there by anyone at any stage, so to me doesn’t add any value or provenance, but it may to someone else

The original tag will tell you things like the gearbox type, carb, accessories like alternator/generator

According to AKD5103, the code 12H241 means:
12 - 1275
H - transverse
241 means the below:
Yd mechanical fuel pump
Ub Lucas C40 dynamo
Hf ??
Ud crankcase ventilation
Sb ??
Ne ??

It's a 1976 - 1978 vintage block.

Could well be from a 1275GT.

I’m aware the number could be either someone being conscientious or a total red herring. I couldn’t find a reference to 241
It’s on its standard bore, and has matching bearing caps.

Any further thoughts?

Or has Spider gone definitive

Does it has a hole or no hole on the casting above the centre main ?
“Holeless” blocks are rarer and I’ve found them on later cars >75/76 .
Not sure if all late 1275 blocks are supposed to be “holeless”

Cheers
Luís

As Spider says, looks like a late A series block that was fitted with a timing chain tensioner. Some of these blocks have a hole above the centre main and some don't. I've never seen an earlier non chain tensioner 1300 block that doesn't have the hole above the centre main.
Yours doesn't appear to have the casting hole but it's not a very clear photo.
I've got 3 late chain tensioner type 1300 blocks that don't have the casting hole. 2 are definitely allegro blocks going by the engine numbers, the other didn't have an engine no when I got it.

I don’t think this had a tensioner
Is this any clearer or am I misunderstanding where the hole should be

Casting hole would be here

Late A series 1275 blocks that had timing chain tensioner have this extra bulge on the front of the block with an additional bolt hole for the timing cover to fit around the tensioner.