Yemen Rial Large Silver Coin...real?

The coin has a very weakly reeded edge when compared to most "modern" collared strikes.

This could be due to three different causes - one of which is of course "counterfeit". But there are two legitimate things can happen that result in a weak edge.

1. Post strike damage - wear intentional or accidental is the most common.
2. An undersized planchet can at times result in a failure of the metal to spread deeply into the reeds of the collar - but that usually is accompanied by a poor rim and general weakness near the perimeter. Here I see a fairly well made "complete" raised rim with decently strong dentils. So the weakness of the reeds is in my opinion an anomaly.
3. Counterfeit coins struck in an open press (typical in China) which are reeded with ring dies or rotating dies often need to be ground down and end up looking like this.

I would not buy such a coin without a confirmation of weight and specific gravity. I say that in part because I believe this coin has very wide margins (raised rim width) which seems too wide.

This coin HAS BEEN FORGED.

Your coin should weigh 19.75g according to Kraus for the year of 1382-1963.
That reeding is very odd, I dont know if its an optical illusion fromt he photo, but it looks like it "snakes" a little.
Other than that, nothing jumps out to me as caution, the leaves look fine with proper details

Nice coin, it looks real to me except some nicks on the edge. I think the weak reeded edge is a norm of this type of coin. I have the same one without any trail of casting. I don't think a counterfeiter will forge such a cheap coin and do it so nicely.

Weight of my coin is 20.26 grams, was bought at GBP4.20 in 2007 on ebay.

I think he means that they're not made the way modern coins are.

Undersized planchet or loose collar can make the edge look terrible. So a close surface inspection is critical in this case. There are well made forgeries so caution is advised.

What type of apparatus did you use to confirm 72% silver? Specific gravity of 72% is one thing but an XRF of 72% is different. I would expect that with XRF there should be a reading just above 72% because of strike enrichment. An exact match between XRF results and the "standard" employed - is very rare from a surface reading.

When a coin is struck the silver flows to the outer surfaces enriching the surface slightly and the copper recedes. So a 73 or 74 reading would be more expected than 72 which makes me think the coin could actually test at 700 fine not 720.

But as someone pointed out - Modern is NOT a word to use in relation to most Yemeni issues. I am not aware of how likely it is that a Yemeni coin could be debased at the mint by 20 points. That needs to be verified.