What Bultaco barrel is stamped 157?

[David Lahey]

I have an orphan Bultaco barrell that I'm not sure what it is. The head is stamped 157. One model reference chart I checked said that M157 is a 125cc Sherpa T and another reference chart told me it is a prototype 238cc Lobito.
The bore is 72mm and it has bridged inlet and exhaust ports. It is a square barrell with no finger boost ports and a 27mm inlet tract. The sleeve protrudes above the aluminium (ie a non-gasket head joint). To me it looks like a mid 1970s 250 Sherpa T or 250 Alpina barrell.

[Moto]

Hi,
   Just a guestamate,but I think it might be a barrel from a 158 Sherpa T.
    The 157 was the prototype bike just before it.
    It has the Sherpa T 27mm inlet tract.
   The std bore for a 158 would have been 71mm?(238cc) Might also be the same barrel for an Alpina 238cc of around the same time.(M165)