Not an emergency yet, need a tank stand expert

[IAReefer]

I wouldn’t trust it. Water is 8.34lbs per gallon x 55 gallons = 459. That’s just water. Add your 120lbs of rock and sand, and you’re up to 579lbs. Add your tank weight and miscellaneous, and knowing how things are actually built that utilize “those round lock things”.
Easy enough to run to Home Depot, grab some 2x4’s and build it. Wrap it in something that looks nice and add an access door/shelf/etc.

 

[Flippers4pups]

I think you'll be fine. The stand was made for a tank that size. Reinforcing it would give you some peace of mind.

 

[Dragon52]

Here's pics of the door open, the small shelf and then open down to the sump. When I bought the stand it had a 55 gallon 1/4" glass on it. My concern is the heavier tank.

You can brace it as described above. It looks like it belongs on it to be honest.