A friend was recently given what looks to be a genuine Patek watch, but we're not sure of its provenance. Let me describe it: men's stainless, black face, silver roman numerals, no date, relatively small diameter. Very thin. No second hand. Hour and minute hands each have a small circle about halfway along their length. On the back it says: Patek Philippe, Geneve, Geneve depuis 1839, All Stainless Steel, Water Resistant, WB-3878M, 100368. It has the Patek seal. It is not a hand wound watch, but I can't hear any evidence of it being automatic and it doesn't say one way or another.
Grateful for any suggestions or insights as to authenticity and value.
thanks.