Question About 1977-D Washington Quarter - Struck on a 40% Silver Planchet

Hi All of you CT Experts,
I was sorting by date my US coins collection and saw a 1977 Washington Quarter (among a lot of them I have) wich called my atention. I figured out that coin did weight 5.71 grs. After, I did weight all others I have and all of them weight from 5.54 to 5.63 grs. To confirm precision of my scale, I did weight a 1776-1976 s Silver Washington Quarter (40% Silver Planchet) and the weight is 5.71 grs.
My question is: Is there possible the existence of a 1977 Washington Quarter (Philadelphia) struck on a 40% Silver Planchet? Or a 1977 (D no D) Washington Quarter (Mint Error)??
I ask it because there is actually only one or two known pieces of it.
I took pictures of my coins to show you.

My 1977 coin "overweight"

Regular circulated coin to verify the scale

And a 1776-1976 to confirm the weight of a 40% Silver clad Planchet

Any comments are appreciated.

 

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CuNi clad Washington quarters weigh 5.67 grams with a tolerance of ± 0.227 grams. Your coin is well within normal tolerances. Weigh enough other quarters, and you'll likely find several that are even heavier.

Edit to add: just weighed four quarters that I found on my desktop:

1976-D, XF: 5.60g
1976-P, VF: 5.72g
1974-P, AU: 5.90g
2019-W, AU: 5.70g

It may be reading a bit high, but it shows the range you can expect.

 

It’s normal and there is a different look for it containing silver. You’ve got a slightly heavy clad quarter.

 

So, after post I weighed another coins of different dates and found different weights, as well.
Thanks @jeffB and @Collecting Nut for your comments.

 

A better picture of the edge would be helpful to tell whether it is 40% or plated.

It appears cu/ ni however.

 

You’re welcome and don’t be such a stranger.

 

All normal coins.

 

Would the Kleenex Tissue method help?

 

Yes, but not for this coin.

 

Clad sorry!

 

Wish I could Like this a thousand times. I'll settle for voting Best Answer, and bookmarking it so I can post it in every other thread that shows confusion about weights.

 

Thank you very much @expat for this weights tolerance list. It will help me ever, and probably will help a lot of others collectors too.

 

A 40% silver 1977 D could exist but not a 1977 plain. Weight is not good enough to tell a clad from a 40% silver, the weight tolerances are large enough that they overlap significantly.