Proper way to call a model constant in Magento 1

echo Company_Module_Model_Somemodel::SOME_CONST;

This one is way to go because Magento uses an autoloader and your class will be autoloaded by name

For further detail please check the reference link https://stackoverflow.com/questions/16792370/proper-way-to-handle-model-constants-in-magento

I hope this will help