Board Fit and Signal-Duty Ratings
The tin-plated post (100.0 µin) is the solder-tail finish; the gold is only on the mating interface where it matters.
The square pin (0.025" sq typical for this series) gives four contact points in the receptacle.
Cross-Shop Against 1376779-2
The difference: 1376779-2 uses 8.00 µin gold (thinner) and ships in Box packaging vs Bulk. For applications requiring maximum mating cycle life, the 15.0 µin gold on this 9-146252-0-09 is the better choice.
