According to what we read in footnote #2 of [I], no portrait of Christian Goldbach seems to be known. The author of the article under consideration even adds:
... Juskevič & Kopelevič's biography states that none exists [J&K, Christian Goldbach: 1690–1764 (translated from Russian to German by Annerose and Walter Purkert, Vita mathematica, Band 8). Basel: Birkhäuser Verlag, 1994, p. xi], also confirmed by Gerald Alexanderson (personal communication) and Goldbach conjecture expert Yuan Wang (personal communication), who explained that Goldbach was not famous at the time... But Goldbach did in fact eventually attain high rank in the Russian government, first as tutor to the crown prince, then later rising to privy councilor... He was also important for many years at the Petersburg Academy, which did include artists (including both Euler’s brother and the father of Euler’s wife). I therefore hope that a picture might yet be found, though perhaps in a government or art historical collection rather than in scholarly archives. As motivation, I hereby offer a bounty of $100 for the first authentic picture of Goldbach (or complete correct proof of the Goldbach conjecture) that I receive!
On the other hand, it is not rare to find web sites on the internet (e.g., 1) http://eljjdx.canalblog.com/archives/2012/08/05/24787409.html, 2) http://images.slideplayer.com.br/3/382572/slides/slide_5.jpg, 3) http://gaussianos.com/la-conjetura-debil-de-goldbach-coloquio-de-harald-helfgott-en-el-icmat/, 4) http://paginas.matem.unam.mx/cprieto/index.php/es/matematicos/matematicos-f/126-goldbach-christian, 5) http://www.alasayvan.com/bilim-adamlari/400020-christian-goldbach-kristiyan-goldbah-ve-matematige-katkilari.html) that imply that Christian Goldbach was this fellow:
It follows that either Mr. Haas's sources are somewhat obsolete or the individual in the portrait is actually not Christian Goldbach.
What do you people know about this matter?
By the way, this theme has made me recall an amusing 2009 note in the Notices of the AMS about a similar situation related to a portrait that for many individuals in the past was A. M. Legendre's (cf. [II, pages 1440-1443]).
[I] R. Haas. Goldbach, Hurwitz, and the infinitude of primes: weaving a proof across the centuries. Math. Intelligencer, Vol. 36, #1, 2014, pp. 54-60.
[II] P. Duren. Changing faces: The mistaken portrait of Legendre. Notices of the AMS, Vol. 56, #11, 2009, pp. 1440-1443.