What does "E21" mean? Thank you

Here's the US contact info Hitachi High Technologies America, Inc. San Francisco Office 5100 Franklin Drive, Pleasanton, CA94588-3355 TEL 1-925-218-2800(Main Phone) TEL 1-800-548-9001(Customer Support) FAX 1-925-218-2900 But It looks like only the UK site support this unit. Hitachi High-Technologies Corporation Department Scientific Instruments Paul Gadsby 7 Ivanhoe Road Hogwood Lane Industrial Estate Finchampstead, Wokingham City Berkshire Zip-code RG40 4QQ Country United Kingdom Phone +44 118 932 8632 Fax +44 118 932 8779 Email paulg@hitachi-hitec-uk.com [url=http://www.hitachi-hitec.com/global/science/index.html]http://www.hitachi-hitec.com/global/science/index.html[/url] We offer the statement-of-the-art technologies and service for you as a specialist of scientific instruments. UV-Visible/NIR Spectrophotometer(UV-Vis) Fluorescence Spectrophotometer (FL) Atomic Absorption Spectrophotometer (AAS) High-Performance Liquid Chromatograph/Amino Acid Analyzer (HPLC/AAA) Clinical analyzer Ultracentrifuge Centrifuge Potentiometric Titrator Karl Fischer Titrator Mercury analyzer