Tinplate photo - for dating please

[Pennant]

My great-aunt left my mother a lot of family family photographs and it wasn't until this year that she showed them to me. My mum can pick out quite a few of the people, and some of them are labelled. However there are some mysteries. Assuming they are all my great-aunt's family, I am trying to match them to people in my tree. Her father was one of 6 boys and I wonder if these were two of them.
There is nothing on the back at all. This branch of the family came from the Portmadog area of Caernarfonshire.
Thank you for any help you can give.

[Hollander]

I have a 'tintype' image of my great grandfather, taken in a studio setting similar to this, in which he is wearing clothing resembling that of these two subjects.
Mine can be dated to the late 1870s - to be precise, March 1879, the occasion of gt. grandfather's 21st birthday.

[Pennant]

Thank you very much. That's really helpful.

[jim1]

The start date is mid 1860's but more likely 1870's.

[Pennant]

Thanks for that. My great grandfather's oldest brother was born in 1851, so mid-60s wouldn't have fitted. But some time in the 70s fits with a few of the brothers, including my great grandfather if it's late 70s, as Hollander said.

[jim1]

I don't believe this is late 1870's.
The younger chap on the left is dressed in a late 1860's-mid 1870's style
which is when styles changed.
Young men always wanted to appear as fashionable as they could.

[Treetotal]

I agree with Jim.
Carol

[Pennant]

I don't believe this is late 1870's.
The younger chap on the left is dressed in a late 1860's-mid 1870's style
which is when styles changed.
Young men always wanted to appear as fashionable as they could.

Roughly how old do you think he is?

[jim1]

I think both in their 20's with the one on the right being the younger.