Now, now - an authentic Reuben is & always has been made with corned beef, not pastrami.
aww breezy, you disappoint me.
you should know that the origin of the reuben is disputed, and even the type(s) of meat used has several different stories behind them. there may be an authentic version with a specific meat, but it's all subject for debate.
it was either invented in nyc, by a deli owner named arnold reuben. or it might have been invented by reuben kulakofsky, of omaha nebraska. and then it gets complicated from there.
there are various stories, interviews, and reports from both origins; granted, the most common uses corned beef. but then there's pastrami, virginia ham, smoked turkey, or even roast beef.
even the type of rye bread is up for debate. regular or dark rye? seeded or not? getting deeper into it, there's debate about if it should be sauerkraut, or cole slaw.
largely, there's the followers of the idea, such as yourself, that a reuben sandwich is stricly corned beef, thousand island, sauerkraut, and swiss on regular rye. in contrast, a "reuben's special" is any of the aforementioned breads, meats, or toppings, assembled the same way as the sandwich.
i've heard that when using pastrami or smoked turkey, you're really having a rachel, not a reuben.
and on it goes.
(btw, you all might have guessed that i love reubens. or rachels. or reuben specials... sheesh
)