Hi ~ welcome to the forums. It's not rare, have seen a good number of them over the years, produced by Watrous Mfg., period advertising shows it was marketed by Wm. Rogers Mfg. - at the time, William H. Watrous was president of both concerns. It was designed in 1896 by Isabella Beecher Hooker, Harriet Beecher Stowe's half-sister, she applied for a design patent in 1897, it was granted in 1898 (#D29866) and witnessed by William H. Watrous. Can't recall ever seeing this spoon in silverplate or bearing a Wm. Rogers mark, though a post on this old thread seems to insinuate that they exist:
http://www.925-1000.com/forum/viewtopic.php?t=9485
~Cheryl
1897 ad, noting the spoon as 'Sterling Silver, 925-1000 Fine':
