Military map symbol for a land unit or formation.
The proper shape of the armoured icon is supposed to be a lozenge shape, but an oval shape is often substituted, likely because it is easier to create in the draw function of many word processors. The oval depiction even appeared in US and Canadian doctrine standards for map symbols: 
- US Army's FM 1-02 Operational Terms and Graphics September 2004

- Canadian Army's B-GL-331-003/FP-001 Military Symbols for Land Operations addendum 27 June 2005
Own work
CdnMCG