score:5
Joseph B. Tyson (Marcion and Luke-Acts, page 24) says that almost everything we know about Marcion comes from polemics written by heresiologists in the second to fourth centuries, particularly Irenaeus. Neither Marcion nor Justin Martyr has left any extant writings that could connect the two in any meaningful way.
Irenaeus (Against Heresies, iv.6) mentions a book by Justin Martyr 'Against Marcion', but this fragment scarcely suggests contact - in fact the reference to 'Against Marcion' suggests estrangement. Justin Martyr's First Apology, chapters 26,58 are also polemics against Marcion. Tyson points out (ibid, page 29) that in the First Apology, written about 150 CE, Martyr expresses no knowledge of Marcion's activities in Rome nor about his excommunication from the church there, saying that what is striking is that Justin Martyr is surprised that Marcion is still teaching. All this points to Martyr's knowledge of Marcion to be by reputation, rather than personal contact.
The estimated range of dating for the works of Justin Martyr is 150-160 CE, which would mean they were written towards the end of Marcion's lifetime. Whether any of these reached Marcion and whether he chose to read them is unknown. It is reasonable to assume they had no personal contact, either directly or indirectly.