The weight is correct. The planchet is correct (IMO). I doubt if it's silver plated. I've seen many of these. For whatever reason, the copper clad doesn't always show thru on the edge. Someone else can explain the numismatic technical reason for that you're seeing.
Most likely the quarter has either been plated as a novelty item after it left the mint, or a dull punch has pulled the cupronickel cladding over the edge while punching blanks from the coil. The weight of a Silver Clad Quarter, adjusted for tolerance, is too close to the weight of a Cupronickel Clad Quarter, adjusted for tolerance, to identify the type of cladding. Quarter 1947-1964 = 6.250 g +/- 0.194 g (900 Ag 100 Cu) Weight of Clad quarter 1965 – to present = 5.670 g +/- 0.227 g (75 Cu, 25 Ni on pure Cu) (1976 = 5.750 g +/- 0.200 g - 40% silver clad) A specific gravity test can tell. Specific Gravity Test. 90% Silver = SG 10.34; 40% Silver = SG 9.53 Cupro Nickel clad = SG 8.92 Copper Cent = SG 8.83; Zinc Cent = SG 7.17; Steel cent = 7.7 Here are instructions about how to perform a specific gravity test: https://en.numista.com/numisdoc/determining-the-metal-of-a-coin-27.html Another alternative to determine metal content is via an XRF Scan. For an inexact test: Take a known silver coin and a known clad coin and lay a single ply piece of tissue over them. The silver coin will always appear bright through the tissue. Almost as if it is lit up. Compare with your coin in question.
See if any coin or pawn dealers in your area have a spectrograph There generally is no charge to check an item. They toss it in, close the lid and hit the button. In 3 seconds you get a breakdown of the metals and the percentage of it. I also had a silver appearing quarter. Took no time to learn I am still poor.
I'v tried these method's maybe they will work for you on checking for silver content or fake silver. Hope it helps http://opencurrency.com/3-quick-ways-to-help-tell-real-silver-from-fake-silver/
For an inexact test: Take a known silver coin and a known clad coin and lay a single ply piece of tissue over them. The silver coin will always appear bright through the tissue. Almost as if it is lit up. Compare with your coin in question. this WORKS//
I've seen more ads for platinum-plated than silver-plated quarters. Brought to you by the same clowns who gold-plate them. A platinum layer would be too thin to affect the weight in a measurable way, and would presumably fail the tissue test (not as reflective as silver).