Very good quads and impressive that you're still getting gains in your mid-50s 
Mind telling how you train your quads?
When I first started lifting in mid- teen years my legs blew up easily. Then I neglected them for decades. Only extensions. No heavy lifting presses or squats.
I started training them hard again around 48 years old. I came across a video on YT of Jeff Kings leg routine and copied it. I liked his routine because he didn't do back squats- which can throw out my lower back without warning.
So my routine is:
1. leg extensions- a lot of them. Start with light weight to warm up my knees. Probably 7 to 8 sets of extensions.
2. Then Front Squats- about 6 sets of 10 to 15 reps each. Up to 185, sometimes as high as 225 .
3. Then Hack Squats- moderate weight. Ive gone as high as 7 plates but usually five 45 lb plates.
4.Then the vertical leg press- 4 sets of ten.
5 & 6 Finish with calf raises and alternating with leg curls. 4 sets of 15 reps for each exercise. I have a throry about calves. I only use the machine that allows me to stand. Not the seated calf raise. It could be bro-science but Im pretty sure the standing machine engages more secondary muscles that build the calves better.
There's all these hot gym babes that always fucking squat or deadlift. One day the hottest girl in the gym walked over and put 135 on the bar and knocked out 10 reps of front squats no problem. I said to myself " if a fucking girl can do it, you have no excuses. That was 3 years ago.
$20 to workout?
Ridiculous.
Agreed. I get a discount and pay 14. Still ridiculous.
impressive legs! Do they have a safety squat bar or spider bar?
They have so much equipment in there its more of a warehouse of random equipment, including original Nautilus machines- the kind Boyer, Mike and Ray used in those old videos. Hex bar. Numerous squat racks. Not sure what a spider bar is but they dont have the leg blaster thing that Zane used to use.
Was Ed Coan's home base for many years, filmed his training tapes there -
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P.S. - Impressive quads, compression not withstanding.
Thanks! Eds pictures are all over the gym. But EVERYONES is. Every bodybuilder you can think of from the 80's and 90's. Place is like a museum of bodybuilding.