I have a poster from Nicholas & Lefever referring to breech loading shot guns I am looking for information about it. It has a 1971 The wentworth press in the bottom rt side of the print

Hello, Charlotte -

Are you perhaps trying to find a sale or insurance valuation for your poster? Or, do you wish to know more about the Nicholas & Lefever firearms company? Or more about their breech loading shotguns?

Fixya.com, a website intended for asking and answering questions on how to go about REPAIRING THINGS, probably is not the best website for your question. Plus, your question landed in the Fixya category for Optics - nothing to do with advertising posters. :)

I did find what I think is a duplicate of your poster for sale on the eBay United Kingdom web site:
TinyURL link:
https://tinyurlcom/yae2q7n5

The size of the poster seems to be a reprint (reprint made in 1971) of what may be either a full-page newspaper advertisement or a full-page magazine advertisement. The selling price from the eBay page is $45.00 Australian dollars / £25.25 (equivalent of $35.40 - $35.24, US dollars; Source or currency conversion:
http://www.xe.com/currencyconverter/ )

Apparently the firearms company Nicholas & Lefever, Syracuse, New York, existed from 1876-1879.
Sources:
Lefever Arms Collectors Association:
http://www.lefevercollectors.com/index.php?p=1_8_History-Of-D-M-Lefever
and
"Lefever Arms - An American Iconic Maker", James D. Julia Auctioneers
http://jamesdjulia.com/emails/gun_newsletter_9-13-2016.htm
(Column 1, Paragraph 2)

If you wish to know more about the company and their firearms, the Onondaga (County) Historical Association, Syracuse, New York may be able to provide you with more information on the company.
Onondaga Historical Society home page:
http://www.cnyhistory.org/

If you cannot visit the Onondaga Historical Assoc. Research Center yourself, there is a charge for their research. See:
http://www.cnyhistory.org/explore/research/

Note: I am a librarian by profession and have answered library client questions about posters, paintings, antiques, etc. over my 40+ year career.

Best wishes.