Hi, I´m not a specialist on these but as a general rule try to buy only a watch that has been purchased, reviewed and pictured by a member. That way You get to see what is otherwise "hidden" or not mentioned. Skip the others.
1:1 and used a genuine doesn´t mean too much either in relation to the gen because of limitations in caseset thickness or dial position, although it does imply that other models are better.
For this specific watch I would go with the somewhat similar OS20 quartz version, these are normally microsteppers so the chrono seconds should sweep, it´s the FM046c if You search on the site with "same caseset as the A7750" version, which is generally a good sign. As nothings breaks, squeaks or rattles on a quartz, I find them often to better replicate a gen feeling and reliability, but that´s just my opinion.