Many Thanks to Taryn Greg and Roger for the excellent help they gave me. Check out their web sites - most interesting and informative.

I found out it was a Cabinet Card from Taryn 
Hi Ron 
It appears you have a Cabinet Card, which was introduced in 1866 and fell out of favour about 1910. I would say that it is from the late 1860s, judging by
the woman's dress and the boy's outfit. I'd say the woman is in her early 40s and the boy about 8 or 9. I'm not great at ages! 
So, I'd say that the photo is an early Cabinet Card, probably 1866/67 era.  
Taryn www.geocities.com/cartedevisites.

Greg gave me some great comments on fashion etc and that it was a copy 
Ron - I probably couldn't do better than the estimate you have of 1868-1871 for the clothes, though I think it could be as early as 1865. I would guess it is probably a reprint done in the late 1870s or early 1880s of a photo taken ten years or more before.

The drapes and plain background are classic 1860s. The woman's bonnet is probably already old-fashioned at the time of sitting and possibly harks back to the early 60s or even 50s. The boy's frock coat is done up at the top in the style of the mid 1860s. His hairstyle is also consistent with the 60s. Her hairstyle, like her bonnet, is old-fashioned if the photo was taken 1868-71. The centre part with hair over the ears was more common 1855-1865. But hairstyle in any decade is idiosyncratic and you can never tell how much a person followed fashion. Older women often did their hair the same way they had twenty years earlier.

Round corners came in at the very end of the 70s. Cabinet-size photos were from 1866 on, but did not become common until the 1880s. Are you sure it's not a
On my website I have some examples of fashions in photographs, etc - http://www.acay.com.au/~gsm/photo-dates.html
regards,  Greg M

Roger I think gave the Final Answer
Hi Ron I think your photo "E.C.Porter" is a later copy of an ambrotype or daguerreotype of 1859 based on the clothes.
I agree with Greg - here is my reasoning:   
Ok, the close up look of the photo is the one achieved by earlier formats, typically a daguerreotype and this look was not seen again until about the 1870s - with lens improvements - and so this causes dating confusion - when it is a copy.   The top buttoned jacket goes back as far as 1860 - so my photos show, and before - probably. The bonnet was high fashion 1848 - 50 but an older women could have worn it probably as late as 1862.   Daguerreotype's were produced up to the 1850s (10/6d) when the cheap cost of CDV (1/-) in 1859, drove them out, except for those customers who liked the older format.(£2 was a weeks wage).   So I guess we come to 1859 to 1862 but most likely early 1859.
Roger Vaughan http://www.rogerco.freeserve.co.uk/index.htm