That's a mid 50s Large Stamp Hartrick Type I. The fact that you call it a "Big Stamp" and have "late 50s early 60s" tells me you haven't been looking at reliable sources for your identification. ;)
[img]http://black.net.nz/avedis/images/hb-detail-stamp.jpg[/img]
ref: http://black.net.nz/avedis/avedis-gallery.html#large
Expected prices for cymbals with a Large Stamp are: $200 with half selling for between $120 and $245 n=28
ref: http://black.net.nz/avedis/avedis-prices.html#20
But note that if the weight is 1900g you might do a bit better than $200. If you follow the link above you can see that lower weight does get a small price advantage. Looking into the raw data, getting a price over $350 seems to be based on a fortuitous combination of seller reputation, excellent sound file, quality ad, and a lower than average weight for Large Stamp cymbals. Under 1800g seems to be the added value zone, but I don't have enough data to estimate threshhold effects yet.
The condition of that one may also hold the price down a bit. I can't judge that much from the one small photo, but it looks like there are at least two edge dings or "flea bites". I suspect we're not looking at a cymbal which will get the "excellent condition" price lift. The range I gave above doesn't take condition or weight into account so it is the best estimate if you don't know any other details. So far I'd stick with that range and an expected price of about $200. Of course you can always hold out for a higher price (say $250) and potentially take a lot longer to sell it. That's another tradeoff.
As far as the rivet holes go, having 7 is not as common as 6 or 8 and suggests (but doesn't prove 100%) the holes are post factory. I don't have any evidence that rivet holes (factory or post-factory) have an effect on expected price. It may be that rivet holes lower the price $10 to $15 but my data and statistical modelling can't pick up an effect that small given all the other source of variation due to condition, weight, quality of ad, quality of sound file, reputation of seller, and other factors you might think of like the season you sell it in and the state of the general economy. I acknowledge that some people hold beliefs that rivet holes lower expected price, but their beliefs have not been tested against the evidence as far as I know. I've written a bit about beliefs vs the price evidence in other contexts. See:
http://black.net.nz/old-k/old-k-prices.html#summary