Do I have the 81-244?

If the style and dimensions match up exactly, then there's a good chance the 81-244 is what you have. I'm not comfortable assuming anything in this industry but you can still make a pretty educated guess. 

For example, I can tell you that Pella doesn't really use a wide variety of hardware. In fact, their hardware is very, very specific. There's not going to be a roller similar to the 81-244 but slightly different in some small, subtle aspect like you might find with other brands. The 81-244 is pretty much one of a kind.

So with that in mind, and as long as your measurements are identical to those we show on our site, I think the 81-244 is a good option to consider for your door.