This chipmunk s/n checker thing is a bit rubbish. It appears to be crowd sourced information rather than actual information sourced from the factories. All it really gives you is model type (capacity, colour, etc) which they've obviously figured out how the serial numbers are used (again, crowd sourced information, after one gets a large enough sample, one can deduce which parts of the serial number describes what part of the device). In other words, outside of being able to deduce the basic spec's as well as if it's a replacement stock unit or a retail unit (for the case of the iPad 2, the first few letters for replacement units is always DLX).
Long story short, until Apple starts selling refurbished iPad 2s, sites like the chipmunk site is NOT going to know what the refurbished units' serial number series. On top of that, nobody really knows if things like refurbished iPads (1st gen) really are refurbished or sold as refurbished when in actuality they are deadstock (excess and unsold inventory). We're not really going to know what the refurbished iPad 2s' serial number series are going to be for at least 6+ months to a year from now. There's also always the other problem with crowd sourcing information like this, if enough people assume that their replacement unit is refurbished and then noted that when using something like the chipmunk site, it's going to start showing up on the chipmunk site as the unit being refurbished (again, this is crowd sourced information rather than actual factory/internal database data).
Here's what I got when I put in my iPhone 4's serial number (keep in mind that my iPhone is a brown box replacement unit from week one of release):
Name: iPhone 4 (GSM - UMTS)
Model: iphone_4
Group1: iPhone
Group2:
Generation: 4
ModelCode: iphone_4
Model introduced: 2010
Production year: 2010
Production week: 24 (June)
Production number: 24611 (within this week)
introduced test: 2010 (0) 1
introduced test: GOED
CPU speed: 1.0GHz
Family name: A1332
Screen size: 3.5 inch
Screen resolution: 940x640 pixels
Colour: Black
Capacity: 32GB
Factory: 86 (China)
Pretty useless information if you're trying to figure out if you have a refurb or not. If you want to know if you have a brown box replacement unit, that should be quite easy without having to resort to using sites like Chipmunk because 1) you obviously took your replacement unit out of a brown box and 2) if you compared your original s/n with your replacement, the different serial number series is quite obvious.